How many years will the following take?

a. \($550\) to grow to \($1,049.50\) if invested at 6 percent compounded annually

b. \($37\) to grow to \($63.87\) if invested at 9 percent compounded annually

c. \($110\) to grow to \($398.60\) if invested at 18 percent compounded annually

d. \($56\) to grow to \($89.66\) if invested at 3 percent compounded annually