Consider a permanent-magnet dc-motor with the following parameters: Ra=0.35Ohms, La=1.5mH, Ke=0.5V/(rad/s), Kt=0.5Nm/A, and Jm=0.02kgm^2. The rated torque is 4Nm. This motor is driving a load at a speed of 1500rpm. At some instant, it goes into regenerative braking. Calculate the armature voltage va at that instant, if the current ia is not to exceed 10A in magnitude. Assume that the inertia is large and thus the speed changes very slowly.