(Compound value solving for r) At what annual rate would the following have to be invested? a. $510 to grow to $1,207.36 in 10 years b. $310 to grow to $491.93 in 6 years c. $48 to grow to $518.58 in 21 years d. $216 to grow to $262.55 in 4 years a. At what annual rate would $510 have to be invested to grow to $1,207.36 in 10 years? % (Round to the nearest whole percent.)