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)