The probability that a certain dart player hits the bullseye with one dart is $\displaystyle 0.4$.

a) Find the probability that the player scores at most two bullseyes with $\displaystyle 3$ darts.

b) If the probability of scoring at least one bullseye with $\displaystyle n$ darts is greater than $\displaystyle 0.9$, find the least possible value of $\displaystyle n$.