Correct Answer - A
Shift `Deltax=beta/lambda(mu-1)t`
Shift due to one plate `Deltax_1=beta/lambda(mu_1-1)`
Shift due to another path `Deltax_2=beta/lambda(mu_2-1)t`
Net shift `Deltax=Deltax_2-Deltax_1=beta/lambda(mu_2-mu_1)t` ...(i)
Also it is given that `x=5beta` ...(ii)
Hence `5beta=beta/lambda(mu_1-mu_2)t`
`impliest=(5lambda)/((mu_1-mu_2))=(5xx4800xx10^(-10))/((1.7-1.4))`