In a lightning bolt, a large amount of charge flows during a time of 1.8 10-3

Question:

In a lightning bolt, a large amount of charge flows during a time of 1.8 × 10-3 s. Assume that the bolt can be treated as a long, straight line of current. At a perpendicular distance of 27 m from the bolt, a magnetic field of 8.0 × 10-5 T is measured. How much charge has flowed during the lightning bolt? Ignore the earth's magnetic field.