Answer :
present value of annuity = annual payment * [ 1 - (1+i)^-n ]/i
=>
12500 = 128.04 * [1-(1+9%/12^-n]/9%/12
=>n = 42 payments
present value of annuity = annual payment * [ 1 - (1+i)^-n ]/i
=>
12500 = 128.04 * [1-(1+9%/12^-n]/9%/12
=>n = 42 payments