Consider the following probability mass function (p.m.f.) of a random variable X:

\(p\left( {x,q} \right) = \left\{ {\begin{array}{*{20}{c}} q\\ {1 - q}\\ 0 \end{array}} \right.\begin{array}{*{20}{c}} {if\;X = 0}\\ {if\;X = 1}\\ {otherwise} \end{array}\)

If q = 0.4, the variance of X is___________.