Can someone please help me

Find the maximum value of p= 4x + 5y subject to the following constraints :

Math i have no idea how to do a and b

Margaret is purchasing a house for $210,000 with a 15 year fixed rate mortgage at 4.75% interest she has made a 5% down payment the house is valued at 205,000 and the local tax rate is 3.5% homeowners insurance 600 per year what are her total monthly payment