Consider efficiency of M as X , no. of Days E worked as D. $\therefore$ no. of days M worked= $\frac{D}{2}$
$\therefore$ Efficiency of E=$\frac{X}{2}$
$\therefore$ Contribution(M)=X $\times$ $\frac{D}{2}$ $\times$ 6 = 3XD [ $\because$ he has 6 hour shifts ]
$\therefore$ Contribution(E)=$\frac{X}{2}$ $\times$ D $\times$ 12=6XD [ $\because$ he has 12 hour shifts ]
$\frac{ Contribution(M)}{Contribution(E)}$=$\frac{3XD}{6XD}$=$\frac{1}{2}$