diff --git a/LunExLab/Account/Account.cs b/LunExLab/Account/Account.cs
new file mode 100644
index 0000000..2e04399
--- /dev/null
+++ b/LunExLab/Account/Account.cs
@@ -0,0 +1,18 @@
+namespace Accounts;
+
+// import LunExService.LunEx;
+
+public class Account {
+
+    public long TotalGain(Lot[] lots, int currentPrice) {
+        long total = 0;
+        foreach (Lot nextLot in lots) {
+            total += GainForLot(nextLot, currentPrice);
+        }
+        return total;
+    }
+
+    private long GainForLot(Lot lot, int currentPrice) {
+        return lot.GainAt(currentPrice);
+    }
+}
\ No newline at end of file
diff --git a/LunExLab/Account/Account.csproj b/LunExLab/Account/Account.csproj
new file mode 100644
index 0000000..eb2460e
--- /dev/null
+++ b/LunExLab/Account/Account.csproj
@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+</Project>
diff --git a/LunExLab/Account/Lot.cs b/LunExLab/Account/Lot.cs
new file mode 100644
index 0000000..17ce5e6
--- /dev/null
+++ b/LunExLab/Account/Lot.cs
@@ -0,0 +1,18 @@
+namespace Accounts;
+
+public class Lot
+{
+    private int shares;
+    private long cost;
+
+    public Lot(int shares, long cost)
+    {
+        this.shares = shares;
+        this.cost = cost;
+    }
+
+    public long GainAt(int currentPrice)
+    {
+        return (shares * currentPrice) - cost;
+    }
+}
\ No newline at end of file
diff --git a/LunExLab/AccountTests/AccountTests.csproj b/LunExLab/AccountTests/AccountTests.csproj
new file mode 100644
index 0000000..8ecf500
--- /dev/null
+++ b/LunExLab/AccountTests/AccountTests.csproj
@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+
+        <IsPackable>false</IsPackable>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
+        <PackageReference Include="MSTest.TestAdapter" Version="2.2.8" />
+        <PackageReference Include="MSTest.TestFramework" Version="2.2.8" />
+        <PackageReference Include="coverlet.collector" Version="3.1.2" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\Account\Account.csproj" />
+    </ItemGroup>
+
+</Project>
diff --git a/LunExLab/AccountTests/TotalGainTests.cs b/LunExLab/AccountTests/TotalGainTests.cs
new file mode 100644
index 0000000..3c491d4
--- /dev/null
+++ b/LunExLab/AccountTests/TotalGainTests.cs
@@ -0,0 +1,24 @@
+
+using Accounts;
+
+namespace AccountTests;
+
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+
+[TestClass]
+public class TotalGainTests
+{
+    [TestMethod]
+    public void WhenUsingInteger()
+    {
+        // given
+        var firstLot = new Lot(100, 3000L);
+        var latestLot = new Lot(10, 400L);
+        Lot[] lots = { firstLot, latestLot };
+        Account account = new Account();
+        
+        // when/then
+        Assert.AreEqual(1220L, account.TotalGain(lots, 42));
+    }
+}
\ No newline at end of file
diff --git a/LunExLab/LunExLab.sln b/LunExLab/LunExLab.sln
index e0bc31a..841997a 100644
--- a/LunExLab/LunExLab.sln
+++ b/LunExLab/LunExLab.sln
@@ -2,6 +2,10 @@
 Microsoft Visual Studio Solution File, Format Version 12.00
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "LunExService", "LunExService\LunExService.csproj", "{CCFD3F57-923D-4665-AAAC-3475217E9ADB}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AccountTests", "AccountTests\AccountTests.csproj", "{E0E46080-7AAA-4D15-96DD-26A40CBA3DFA}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Account", "Account\Account.csproj", "{F09891BE-9441-4234-8A61-9587D8221F42}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -12,5 +16,13 @@ Global
 		{CCFD3F57-923D-4665-AAAC-3475217E9ADB}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{CCFD3F57-923D-4665-AAAC-3475217E9ADB}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{CCFD3F57-923D-4665-AAAC-3475217E9ADB}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E0E46080-7AAA-4D15-96DD-26A40CBA3DFA}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E0E46080-7AAA-4D15-96DD-26A40CBA3DFA}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E0E46080-7AAA-4D15-96DD-26A40CBA3DFA}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E0E46080-7AAA-4D15-96DD-26A40CBA3DFA}.Release|Any CPU.Build.0 = Release|Any CPU
+		{F09891BE-9441-4234-8A61-9587D8221F42}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{F09891BE-9441-4234-8A61-9587D8221F42}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{F09891BE-9441-4234-8A61-9587D8221F42}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{F09891BE-9441-4234-8A61-9587D8221F42}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal