During a Morse test on a 4 cylinder engine, the following measurements of brake power were taken at constant speed.
All cylinders firing3037 kW
Number 1 cylinder not firing2102 kW
Number 2 cylinder not firing2102 kW
Number 3 cylinder not firing2100 kW
Number 4 cylinder not firing2098 kW
The mechanical efficiency of the engine is
(a) 91.53% (b) 85.07%
(c) 81.07% (d) 61.22%