please answer both :)

21. A local bank is offering 6%, compounded semi-annually, on savings accounts. If you deposit $4,000 today, how much will you have in 2.5 yrs. 20. If you presently have 40,000 dollars invested at a rate of 21 percent, compounded annually, how many years, to the closest year, will it take for your investment to triple? It must triple. a. 6 years b. 7 years c. 8 years d. 5 years e. 4 years