Select the option that represents the letters that, when placed from left to right in the blanks below, will complete the letter series.
P_T P_S_C T_R S P C_P R_P_T _R S
If '+' means '-', '-' means 'ร', 'ร' means '+', and 'รท' means '+', what will come
in place of the question mark (?) in the following equation?
28 - 2 + 80 ร 5 รท 14 = ?