Consider the following probability mass function (p.m.f.) of a random variable $X$ : $p(x, q)=\left\{\begin{array}{cc}
q & \text { if } X=0 \\
1-q & \text { if } X=1 \\
0 & \text { otherwise }
\end{array}\right.$ If $q=0.4$, the variance of $X$ is
Consider the following probability mass function (p.m.f.) of a random variable $X$ : $p(x, q)=\left\{\begin{array}{cc}
q & \text { if } X=0 \\
1-q & \text { if } X=1 \\
0 & \text { otherwise }
\end{array}\right.$ If $q=0.4$, the variance of $X$ is