$1.$ A dc machine is operating under the conditions such that Ka $=0\mathrm{.}1$ Volts $/$rpm$.$ The developed torque is $80$ N$-$m$.$ The armature resistance Ra $=0\mathrm{.}12$ ohms.$$ If the terminal voltage is $250$ volts, find the speed of this machine when it is operating as a motor and as a generator. $($ Ans: $2,400$ rpm and $2,600$ rpm$)$

The answers are given, I just cant figure out how to arrive at that answer. Use the basic equation like P$\_$o$=$Tw $,$ E$\_$b$=$kw etc