A separately excited DC motor rated 400 V, 15 A, 1500 RPM drives a constant torque load at rated speed operating from 400 V DC supply drawing rated current. The armature resistance is 1.2 $\Omega$. If the supply voltage drops by 10% with field current unaltered then the resultant speed of the motor in RPM is \underline{\hspace{1cm}} (Round off to the nearest integer).