I don't get I to solve these two questions

Question 18 A solenoid 91.6 cm long has 660 turns and a radius of 2.65 cm. If it carries a current of 3.91 A, find the magnetic field along the axis at its center. Answer in units of T. Question 15 A rectangular loop consists of 233 closely wrapped turns of wire and has dimensions 0.79 m by 0.5 m. The loop is hinged along the y-axis, and its plane makes an angle of 43 with the x-axis. A uniform magnetic field of 0.34 T is d rected along the x-axis and the current in the loop is 9.4 A in the direction shown. What is the magnitude of the torque ex- erted on the loon Answer in units of N . m