Let X be a non-negative integer valued random variable. Observe X items and mark each of the X items independently with probability s where $\displaystyle 0<s<1$. What is the probability that all X items are marked?

Solution so far:

On the surface it looks like $\displaystyle Pr[all \ items \ marked ] = s^X $, but I know there is no way this can be this easy... What am I doing wrong?