Calculate the percentage efficiency at rated load


The following data applies to a 100kW, 250V, 6 pole, 900 RPM,long-shunt, compound DC generator: No-load rotational loss = 3,480Watts
Armature resistance = 0.012 ohms
Series field resistance = 0.008 ohms
Shunt field current = 2.6 A
Assume a stray-loss equal to 1% of the output. Calculate the %efficiency at rated load.
The answer becomes 92.2% but please show the steps arriving to the answer.