Coil 1 is a fl at circular coil that has N1 turns and a radius R1. At its center is a much smaller flat, circular coil that has N2 turns and radius R2. The planes of the coils are parallel. Assume that coil 2 is so small that the magnetic field due to coil 1 has nearly the same value at all points covered by the area of coil 2. Determine an expression for the mutual inductance between these two coils in terms of μ0, N1, R1, N2, and R2.