# $X$ is a random variable taking the values $3, 4$and $12$ with probabilities $\large\frac{1}{3},\frac{1}{4}$ and $\large\frac{4}{7}.$ Then $E(X)$ is
$\begin{array}{1 1}(1)5&(2)6\\(3)7&(4)3\end{array}$