Answer:
Why?:
The interest formula is A = P(1+r/m)^mt
A is the Amount, P is principal (initial investment), R is rate, M is times per year (not used) and T is time.
So if we want 1000 = 800(1+r)^4, we need to find R. In this case, R is about 5 percent. (I'm not super confident, so see if you have other answers)
