diff --git a/HelloStudents/HelloStudents.csproj b/HelloStudents/HelloStudents.csproj
index 8117afe..23de553 100644
--- a/HelloStudents/HelloStudents.csproj
+++ b/HelloStudents/HelloStudents.csproj
@@ -49,6 +49,7 @@
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Student3099Ham.cs" />
+    <Compile Include="Student3115Lee.cs" />
     <Compile Include="Student3108Kim.cs" />
     <Compile Include="Student3103Kim.cs" />
     <Compile Include="Student3116JO.cs" />
diff --git a/HelloStudents/Program.cs b/HelloStudents/Program.cs
index 019bc19..2e676e4 100644
--- a/HelloStudents/Program.cs
+++ b/HelloStudents/Program.cs
@@ -3,7 +3,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using System.Threading.Tasks;
+using System.Threading.Tasks; //import
 
 // namespace는 java의 패키지 같은 역할
 namespace HelloStudents
@@ -46,7 +46,7 @@ static void Main(string[] args)
                    BaseYear = 2020
                });
             // 3104
-            // 3105
+            // 3105     
             // 3106
             // 3107
             // 3108
@@ -65,6 +65,14 @@ static void Main(string[] args)
             // 3113
             // 3114
             // 3115
+            students.Add(
+                new Student3115Lee()
+                {
+                    FirstName = "지민",
+                    LastName = "이",
+                    StudentNumber = 3115,
+                    BaseYear = 2021
+                });
             // 3116
             students.Add(
                 new Student3116JO()
diff --git a/HelloStudents/Student3115Lee.cs b/HelloStudents/Student3115Lee.cs
new file mode 100644
index 0000000..6b26c00
--- /dev/null
+++ b/HelloStudents/Student3115Lee.cs
@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace HelloStudents
+{
+    class Student3115Lee : StudentBase
+    {
+        public override string Hello()
+        {
+            return "안녕? 나는 " + this + "이야~~~~~~~~~~~~~~!";  //this는 this.ToString()과 같다. 
+        }
+    }
+}
diff --git a/HelloStudents/StudentBase.cs b/HelloStudents/StudentBase.cs
index c592409..c70e0bb 100644
--- a/HelloStudents/StudentBase.cs
+++ b/HelloStudents/StudentBase.cs
@@ -9,7 +9,7 @@ namespace HelloStudents
     abstract class StudentBase : IEquatable<StudentBase>, IComparable<StudentBase>
     {
         // 속성들 (멤버변수와 다름!)
-        public string LastName { get; set; }
+        public string LastName { get; set; } //getter, setter 메서드 생성
         public string FirstName { get; set; }
         public int StudentNumber { get; set; }