A wire of r=1cm consist of 1m steel and 2m copper respectively.Total extension when a force applied is 1mm.Find the force is $Y_{cu}=1.1\times 10^{11}N/m^2,Y_{steel}=2\times 10^{11}N/m^2$.

Question

$\begin{array}{1 1}(A)\;1.46\times 10^3N\\(B)\;1.2\times 10^3N\\(C)\;1.36\times 10^3N\\(D)\;\text{None}\end{array}$