A random variable $X$ has the following probability mass function as follows:\[\]$\begin{array} {llllllll} \textbf{X:}& -2& 3 & 1 \\ \textbf{P(X=x):}& \large\frac{\lambda}{6}& \large\frac{\lambda}{4} &\large\frac{\lambda}{12} \end{array}$\[\] Then the value of $\lambda$ is
