Really need help on these homework questions

1. An amount of P dollars is borrowed for the given length of time at an annual interest rate of r. Find the simple interest that is owed. (Round your answer to the nearest cent.)

P = $2100, r = 8.0%, 3 months

$___?___

2. An amount of P dollars is borrowed for the given length of time at an annual interest rate of r. Find the simple interest that is owed. (Round your answer to the nearest cent.)

P = $3200, r = 5.0%, 8 years

$ ___?___

3. An amount of P dollars is borrowed for the given length of time with the amount F due at the end of the given length of time. Find the annual simple interest rate r.

(Round your answer to two decimal places.)

P = $2700, F = 4155.30, 7 years

r = _____ %