Suppose that a shunt-connected machine operates at 800 rpm on the linear portion of its magnetization characteristic. The motor drives a load that requires constant torque. Assume that RA = 0. The resistances in the field circuit are RF = 50Ω and Radj = 25Ω. Find a new value for Radj so that the speed becomes 1200 rpm. What is the slowest speed that can be achieved by varying Radj?