Let X denote the number of hours a student studies on any day. If

$P(X=x)=\left\{\begin{matrix}0,1, & x=0\\ kx, & x=1 & or\, 2\\k(5-x), & if & x=3\, or \, 4\\0, & & otherwise\end{matrix}\right.$

where k > 0 is a constant, then $P(X≥2)$ is equal to :

0.75