The continuous random variable ( W ) has a probability density function ( g(w) ), given by ( g(w) = begin{cases} aw+b, & {for } 0 ≤ w < 4 bw+a, & {for } 4 ≤ w < 5 end{cases} ). Find the values of ( a ) and ( b ) if it is given that ( P(2 ≤ W < 4) = {2}/{5} ).