College Physics (4th Edition)

$I = 39~A$
We can find the current $I$ in the solenoid: $B = \mu~n~I$ $I = \frac{B}{\mu~n}$ $I = \frac{(0.24~T)}{(4\pi \times 10^{-7}~T~m/A)(4850~m^{-1})}$ $I = 39~A$