The mean effective pressure of Otto cycle is given by ________.

A

$$p_m = \frac{p_1 r_k(r_p - 1)(r_k^{\gamma - 1} - 1)}{(\gamma - 1)(r_k - 1)}$$

B

$$p_m = \frac{p_1 r_k(r_p - 1)(r_k^{\gamma + 1} - 1)}{(\gamma + 1)(r_k - 1)}$$

C

$$p_m = \frac{p_1 r_k(r_p + 1)(r_k^{\gamma - 1} - 1)}{(\gamma - 1)(r_k + 1)}$$

D

$$p_m = \frac{p_1 r_k(r_p - 1)(r_k^{\gamma + 1} - 1)}{(\gamma - 1)(r_k - 1)}$$