Answer:
15.44 years
Explanation:
Using both excel rate function and financial calculator, the time taken to repay the debt can be computed thus:
Excel rate function:
=nper(rate,pmt,-pv,fv)
rate= interest rate=4%
pmt=yearly payment=c
pv=loan oustanding=-39000
fv=the balance after all payments should be zero=0
=nper(4%,3435,-39000,0)= 15.44 years
Financial calculate
PMT= 3435
RATE=4
PV=-39000
FV=0
CPT N=15.44 years
This means a payment of $3,435 per year for 15 years  and $ 1,511.40  ($3,435*0.44) in the sixteenth year