I need the answers to both questions, show all work, pls

Landon wallin is an auto mechanic who wishes to start his own business. he will need $4400 to purchase tools and equipment. landon decides to finance the purchase with a 48-month fixed installment loan with an apr of 5.5%. a) determine landon's finance charge. b) determine landon's monthly payment.

How do you solve a question like this?

1- what do you think the product of a nonzero rational number and an irrational number is? is it rational or irrational? make use of variables, the closure property of integers, and possibly a proof by contradiction to prove your hypothesis.2- why do we have to specify that the rational number must be nonzero when we determine what the product of a nonzero rational number and an irrational number is? if the rational number were 0, would it give us the same result we found in the first question?