Answer
2 years
Work Step by Step
You can say that the bank is making an investment by lending you money, and expecting
$FV=4640$ for $PV=4000$ at $r=0.008,$ with $t=?$
Simple interest formula:
$FV=PV(1+rt),\qquad $we solve for t.
$FV=PV+PVrt\qquad /-PV$
$FV-PV=PVrt\qquad/\div(PV\cdot r)$
$t=\displaystyle \frac{FV-PV}{PV\cdot t}=\frac{640}{4000\cdot 0.08}=2$
The loan matures in 2 years