Define mutual inductance between a pair of coils. Derive an expression for the mutual inductance of two long coaxial solenoids of the same length wound one over the other.
a) M = μ₀n₁n₂A/l
b) M = μ₀n₁n₂A/(2l)
c) M = μ₀n₁n₂/l
d) M = μ₀n₁n₂/(2l)