A random variable $X$ has the following probability distribution.\[\]$\begin{array} {llllllll} \textbf{X:}& 0& 1& 2& 3& 4& 5 \\ \textbf{P(X=x):}& 1/4& 2a &3a& 4a& 5a& 1/4 \end{array}$\[\]Then $p(1\leq x\leq 4)$ is

Question

\[\begin{array}{1 1}(1)\frac{10}{21}&(2)\frac{2}{7}\\(3)\frac{1}{14}&(4)\frac{1}{2}\end{array}\]