The magnetic field inside a solenoid is 8.617 mT. If this solenoid sits with its central axis perpendicular to a 30 mT magnetic field, what is the magnitude of the torque on the solenoid

Answer 1

For the torque on a solenoid in field B oriented at angle a, see
http://library.thinkquest.org/16600/advanced/magneticfields.shtml

The torque G is given is in terms of N I A, where N is the number of solenoid turns or area A, and I is the solenoid current. See if you can relate that to the solenoid-produced field