A diesel engine does not use spark plugs to ignite the fuel and air in the cylinders. Instead, the temperature required to ignite the fuel occurs because the pistons compress the air in the cylinders. Suppose that air at an initial temperature of 21 oC is compressed adiabatically to a temperature of 688 oC. Assume the air to be an ideal gas for which γ = 7/5. Find the compression ratio, which is the ratio of the initial volume to the final volume?