Show that for a discrete uniform random variable $X$, if each of the values in the range of $X$ is multiplied by the constant $c,$ the effect is to multiply the mean of $X$ by $c$ and the variance of $X$ by $c^{2}$. That is, show that $E(c X)=c E(X)$ and $V(c X)=c^{2} V(X).$