6 years
Step-by-step explanation:
The computation of the time period is given below:
As we know that
Future value = Present value × (1 + rate of interest)^time period
$6,720 = ($35,000 × 15%) × (1 + 0.04)^time period
$6,720 = $5,250 × 1.04^time period
1.28 = 1.04^time period
So, the time period is 6.29 years i.e. 6 years
hence, the time that should be taken is 6 years