Please send me a detailed answer with formula for my review

3.3 a. Juan bought a car with a cash value of P14,000 on the installment plan under the following terms: P4,000 cash upon delivery and the balance payable in 12 equal monthly payments, each payment combining an amortization installment and 6% on the previously unpaid balance Solve for his monthly payment. b. At the end of 8 months, he was forced to sell the car in order to pay a P7,000 debt. At what price must he sell his car so that he can completely pay the car and also pay his P7,000 debt