2.40. Let $X$ be a random variable that takes on only values $1-\frac{1}{n} $ for positive integers $n$. Furthermore, suppose the cdf $F$ for $X$ satisfies $F\left(1-\frac{1} {n} ight)=1-\frac{1}{n}$. a) What is $\mathrm{P}\left(X=\frac{1}{2} ight) ?$ b) What is $\mathrm{P}\left(X=\frac{3}{4} ight) ?$ c) Explain why the set $\{F(w) \mid w