Diesel engines differ from gasoline engines in that the fuel is not ignited by a spark plug. Instead, the air in the cylinder is first compressed to a higher pressure than in a gasoline engine, and the resulting high temperature results in the spontaneous ignition of the fuel when it is injected into the cylinder. 

a. Assuming that the compression ratio is 25:1 (that is, the final volume of the air is 1/25 times the initial volume), that air can be considered an ideal gas with C^∗_V = 21J/(mol K), that the initial conditions of the air are 1 atm and 30^◦C, and that the compression is adiabatic and reversible, determine the temperature of the air in the cylinder before the fuel is injected, and the minimum amount of work that must be done in the compression.

b. The compression ratio in a supercharged gasoline engine is usually 10:1 (or less). Repeat the calculations of part (a) for this compression ratio.