If you deposit $1000 in a savings account with an interest rate of r compounded annually, then the balance in the account after 3 years is given by the function b(c)=1000(1+r)^3 where r is as a decimal. what is the formula for the interest rate, r, required to achieve a balance of b after three years?
a. r=1+(cubroot of b)/10
b. r=-1+(cubroot of b)/-10
c. r=-1+(cubroot of b)/10
d. r=-1+10/(cubroot of b)