The diameter of a shaft is increased from 40 mm to 120 mm, all other conditions remaining unchanged. How many times has its torque carrying capacity increased?

I'm trying to solve this Statics exercise, but I'm getting the wrong answer in every approach I made. How can I solve it?

A motor is used to drive a gear assembly at 200 rpm. The main gear is in the center of a 1 m long (0.5 m to the left and right of the gear) 50 mm diameter solid circular shaft, and power is taken from the two shaft ends. 25 kW is taken on the left end and an unknown amount of power is taken at the right end. the torque to the left side of the gear is? maximum shear stress to left of gear? If the maximum shear stress on the shaft to the right of the gear is 125 MPa, approximately how much power is being drawn off from the right side of the shaft? The shaft can be made from 6061-T6 aluminum. It has adequate strength to withstand the loading conditions in the scenario, including the loading on the right side of the shaft. true or false?

For the steel shaft shown in Fig. Draw a torque diagram for the shaft. 17 ft kip 60 ft-kip 12 ft-kip 10 ft-kip 25 ft-kip