diff --git a/hoseok/gotofjava/src/main/java/chapter05/SalaryManager.java b/hoseok/gotofjava/src/main/java/chapter05/SalaryManager.java
new file mode 100644
index 0000000..aa42a65
--- /dev/null
+++ b/hoseok/gotofjava/src/main/java/chapter05/SalaryManager.java
@@ -0,0 +1,31 @@
+package chapter05;
+
+public class SalaryManager {
+
+    public double getMonthlySalary(int yearlySalary) {
+        double tax = calculateTax(yearlySalary) + calculateNationalPension(yearlySalary)
+                + calculateHealthInsurance(yearlySalary);
+        yearlySalary -= tax;
+        return yearlySalary / 12.0;
+    }
+
+    private double calculateTax(double monthSalary) {
+        System.out.println("tax : " + (monthSalary * 0.125));
+        return monthSalary * 0.125;
+    }
+
+    private double calculateNationalPension(double monthSalary) {
+        System.out.println("national pension : " + (monthSalary * 0.081));
+        return monthSalary * 0.081;
+    }
+
+    private double calculateHealthInsurance(double monthSalary) {
+        System.out.println("health insurance : " + (monthSalary * 0.135));
+        return monthSalary * 0.135;
+    }
+
+    public static void main(String[] args) {
+        SalaryManager salaryManager = new SalaryManager();
+        System.out.println(salaryManager.getMonthlySalary(20000000));
+    }
+}
diff --git a/hoseok/gotofjava/src/main/java/chapter06/InterestManager.java b/hoseok/gotofjava/src/main/java/chapter06/InterestManager.java
new file mode 100644
index 0000000..72f6530
--- /dev/null
+++ b/hoseok/gotofjava/src/main/java/chapter06/InterestManager.java
@@ -0,0 +1,34 @@
+package chapter06;
+
+public class InterestManager {
+
+    public double getInterestRate(int day) {
+        if (day >= 1 && day <= 90) {
+            return 0.05;
+        } else if (day >= 91 && day <= 180) {
+            return 0.01;
+        } else if (day >= 181 && day <= 364) {
+            return 0.02;
+        } else {
+            return 0.056;
+        }
+    }
+
+    public double calculateAmount(int day, long amount) {
+        double interestRate = getInterestRate(day);
+        return amount + amount * interestRate;
+    }
+
+    public static void main(String[] args) {
+        InterestManager interestManager = new InterestManager();
+
+        long amount = 0;
+        int dayCount = 0;
+        for (int i = 1; i <= 365; i += 10) {
+            dayCount++;
+            amount += 1000000;
+        }
+
+        System.out.println(interestManager.calculateAmount(dayCount, amount));
+    }
+}