You have to multiply the probability of 4 hits and 1 miss (0.8^4(1-0.8)) with the number of ways this can happen in:

Miss - Hit - Hit - Hit - Hit

Hit - Miss - Hit - Hit - Hit

Hit - Hit - Miss - Hit - Hit

Hit - Hit - Hit - Miss - Hit

Hit - Hit - Hit - Hit - Miss

p(4 hits)=0.8^4(1-0.8)*5=40,96%

So your answer is right (because 0.2*5=1), but try with another hit rate.