Hello, I need help figuring out how to solve 18, 19 and 20. I know the answers for 18 is A, 19 is D and 20 is D. I just don't know how my teacher got that. Thank you!!

18) Calculate the effective rate for 4.4% interest compounded monthly. Round to the nearest hundredth 18) of a percent. A) 4.49% B) 4.30% C) 4.1% D) 4.6% E) none of these Use 1 = Prt for simple interest to find the indicated quantity. 19) P = $13,500; t = 4 months; I = $517.50. Find r. 19) A) 11.7% B) 7.7% C) 3.8% D) 11.5% Solve the problem. 20) A bank offers a 6% annual interest rate compounded monthly. The periodic interest rate is 20) A) 0.005%. B) 0.05%. C) 0.06%. D) 0.5%. E) none of these