Niobium Metal Becomes a Superconductor (With Electrical Resistance Equal to Zero)when

Niobium metal becomes a superconductor (with electrical resistance equal to zero) when cooled below 9 K.If superconductivity is destroyed when the surface magnetic field exceeds 0.100 T,determine the maximum current a 4.00-mm-diameter niobium wire can carry and remain superconducting.(µ₀ = 4p x 10^-7 T*m/A)

A) 125 A
B) 250 A
C) 500 A
D) 1 000 A