At what annual rate would the following have to be invested?

a. \($820\) to grow to \($1,988.12\) in 13 years

b. \($320\) to grow to \($423.10\) in 6 years

c. \($57\) to grow to \($290.30\) in 18 years

d. \($230\) to grow to \($576.60\) in 5 years