$2.$ A petrol engine having four cylinders and generating powical efficiency of $\backslash (75\backslash \%\backslash ).$ The stroke to crank shaft develops $25$ kW of brake power with a mechance is $1$ MPa $.$ Determine the stroke and diameter ratio is $1\mathrm{.}5$ and the indicated mean effective pre $30,000$ per hour? Also calculate the engine diameter of the cylinder if the number of cycles are $30,000$ per hour? Also calculate the engine capacity in litres.