Solve the below with excel formulas

You borrow a Graduated Payment Mortgage $($GPM$)$ of $$400,000$ with monthly payments and $15-$year term. The annual interest rate is $4\%.$ The lender allows you to pay only $0\mathrm{.}5$ monthly PMT for the first $5$ years and pay full monthly PMT thereafter. In other words, your payment factors are as follows: month $1-$month $60$: $50\%$; and month $61-$ month $180$: $100\%.$ Suppose that the origination cost of the loan is $$5,000,$ please answer the following questions:

$1.$ What is your monthly payment for the first $5$ years?

$2.$ What is your annual effective cost of the GPM if you hold the loan for an entire term?