If someone could help with these questiones

Answer this 30 points and brainliest!

Melissa is purchasing a $160,000 home and her bank is offering her a 30-year mortgage at a 4.9% interest rate. in order to lower her monthly payment, melissa will make a 20% down payment and will purchase 3 points. what will her monthly mortgage payment be? a. $645.98 b. $650.46 c. $662.93 d. $606.69

Ineed with question three. i don't understand how i'm supposed to achieve 3 marks.