Interest = PRT/100
Compound interest = P(1 + (R/100))^T
Where P = Principle ( amount )
R = Rate
T = Time
Since the time is only 1 year, the answer will be the same for both interest and compound interest formulae.
∴ 4000(2)(1)/100 =$80 (This is the interest value)
Note if question ask you what is the total amount after x years, be sure to add the interest with the principle.