Consider the probability distribution function.
$$
\begin{array}{lcc}
\hline x & 0 & 1 \\
\hline \text { Probability } & 0.40 & 0.60 \\
\hline
\end{array}
$$
a. Graph the probability distribution function.
b. Calculate and graph the cumulative probability distribution.
c. Find the mean of the random variable $X$.
d. Find the variance of $X$.