Figure shows two concentric coplanar coils with radii `a` and `b(alt ltb)`. A current `I = 2t` flows in the smaller loop. Neglecting self-inductance of the larger loop,
a. find the mutual inductance of the two coils,
b. find the emf induced in the larger coil,
c. if the resistance of the larger loop is `R`, find the current in it as a function of time.