The simple interest formula is given by I = PRT, where I = interest earned, P = principal deposited to the account, R = interest rate in decimal form, and T = time in years that the principal remains in the account.
a) Solve the formula for R.
b) Use the new version of the formula to find R, the rate of simple interest, given that a deposit of $10,000 earned $5200 in simple interest when left in an account for 9 years. Write R as a percent.