A current of 45 A is passing through an infinitely long wire which lies along the axis of an infinitely long solenoid of radius 1 cm. The magnetic field produced by the solenoid in the direction of the current in the wire is 4 mT. What is the approximate magnitude of the resultant magnetic field at a point 3 mm radially away from the solenoid axis? (Use ( _o=4 10⁻⁷ ~T ~m / A ).)