A cold$-$air$-$standard Otto cycle has a compression ratio of $9$ and a heat input of $0\mathrm{.}641$ kJ $.$ At the

beginning of the compression stroke, $P_1=95$kPa and $T_1=27C.$ The mass of air in the cycle is

$3$ g $,$ and the maximum temperature in the cycle is $1020$ K $.$ Use $c_v=0\mathrm{.}718k\frac{J}{k}g*K,c_p=1\mathrm{.}005$

$k\frac{J}{k}g*K$ and $k=1\mathrm{.}4,$ determine

a$)$ the thermal efficiency.

b$)$ the mean effective pressure in kPa $.$