A $7500 loan at 9% compounded monthly requires three payments at five month intervals after the date of the loan. The second payment is to be twice the size of the first payment, and the third payment...

   A $7500 loan at 9% compounded monthly requires three payments at five month intervals after the date of the loan. The second payment is to be twice the size of the first payment, and the third payment is to be double the amount of the second payment. Calculate the size of the second payment.