(27-31) Suppose the Earth’s magnetic field at the equator has magnitude 0.50×10^−4T and a northerly

(27-31) Suppose the Earth’s magnetic field at the equator has magnitude 0.50×10^−4T and a northerly direction at all points. Estimate the speed a singly ionized uranium ion ( m=238u , q=e) would need to circle the Earth 5.0km above the equator. Can you ignore gravity? [Ignore relativity.]