Calculate the magnitude of the current in the smaller loop when the net magnetic field at the center of the two loops is exactly zero, in terms of the given variables and physical constants.

a) I = μ₀I₁/(2πr)
b) I = μ₀I₁r/(2π)
c) I = μ₀I₁r²/(2π)
d) I = μ₀I₁r/(4π)