diff --git a/dist/app.js b/dist/app.js
index e69de29..fa5b1c1 100644
--- a/dist/app.js
+++ b/dist/app.js
@@ -0,0 +1,31 @@
+"use strict";
+var Department = /** @class */ (function () {
+    // readonly는 프로퍼티를 초기화한 후 수정할 수 없다. 즉, 한번 할당 되면 변경되면 안되는 고유 번호들을 설정할 때 readonly를 사용한다.
+    function Department(id, name) {
+        this.id = id;
+        this.name = name;
+        // private id: string;
+        // private name: string;
+        this.employees = [];
+        // this.id = id;
+        // this.name = n
+    }
+    Department.prototype.describe = function () {
+        console.log("Department (".concat(this.id, "): ").concat(this.name));
+    };
+    Department.prototype.addEmployee = function (employee) {
+        // this.id = '2';  // readonly이기 때문에 error가 발생한다.
+        this.employees.push(employee);
+    };
+    Department.prototype.printEmployeeInformation = function () {
+        console.log(this.employees.length);
+        console.log(this.employees);
+    };
+    return Department;
+}());
+var accounting = new Department('1', 'Accounting');
+accounting.addEmployee('Max');
+accounting.addEmployee('Manu');
+// accounting.employees[2] = 'Anna';
+accounting.describe();
+accounting.printEmployeeInformation();
diff --git a/src/app.ts b/src/app.ts
index 4ab88f1..9bcceb1 100644
--- a/src/app.ts
+++ b/src/app.ts
@@ -15,17 +15,42 @@ class Department {
     // this.id = '2';  // readonly이기 때문에 error가 발생한다.
     this.employees.push(employee);
   }
-  printEmployeeInformation() {
-    console.log(this.employees.length);
-    console.log(this.employees);
+}
+
+class ITDepartment extends Department {
+  admins: string[];
+  constructor(id: string, public admin: string[]) {
+    super(id, 'IT');
+    this.admins = admin;
+  }
+}
+
+class AccountingDepartment extends Department {
+  constructor(id: string, private reports: string[]) {
+    super(id, 'Account');
+  }
+
+  addReport(text: string) {
+    this.reports.push(text);
+  }
+
+  printReports() {
+    console.log(this.reports);
   }
 }
 
 const accounting = new Department('1', 'Accounting');
+const ITaccounting = new ITDepartment('2', ['Max']);
 
-accounting.addEmployee('Max');
-accounting.addEmployee('Manu');
+ITaccounting.addEmployee('Max');
+ITaccounting.addEmployee('Manu');
 
 // accounting.employees[2] = 'Anna';
-accounting.describe();
-accounting.printEmployeeInformation();
+ITaccounting.describe();
+ITaccounting.printEmployeeInformation();
+
+const NewAccounting = new AccountingDepartment('d2', []);
+
+NewAccounting.addReport('Something went wrong...');
+
+NewAccounting.printReports();