Monthly payment-total interest paid

Question

Problem:

A couple has decided to purchase a $120000 house using a down payment of $18000. They can amortize the balance at 10% over 20 years.

Required:

Question 1: What is their monthly payment?

Question 2: What is the total interest paid?

Question 3: What is the equity after 5 years?

Question 4: What is the equity after 15 years?

Note: Explain all steps comprehensively.