A DC series motor has an armature resistance of 0.06 Ω and series field resistance of 0.08 Ω. The motor is connected to a 400 V supply. Thus line current is 20 A when the speed of the machine is 1100 rpm. When the line current is 50 A and the excitation is increased by 30%, speed of the machine in rpm is

A

1100

B

1003

C

837

D

938