A certain clastic conducting material is stretched into a circular loop of 12.0 $\mathrm{cm}$ radius. It is placed with its plane perpendicular to a uniform 0.800 $\mathrm{T}$ magnetic field. When released, the radius of the loop starts to shrink at an instantaneous rate of
75.0 $\mathrm{cm} / \mathrm{s} .$ What emf is induced in the loop at that instant?