There are 4 black balls and 1 white ball in a box. The balls are taken out until the white ball occurs. Black balls return to the box. Find the probability that the experiment stops after exactly 5 tries.
I wonder if I am right in solving this task this way. P(X=k)=(1-p)$^{k-1}$ $\cdot$ p
P(X=k)=0.8$^4$ $ \cdot $ 0.2=0.08192