The Slope of a Country's Production Possibility Frontier Is Equal

The slope of a country's production possibility frontier is equal to ________ and the optimal production point is located where the slope is equal to ________.Assume that output of good Y is measured on the vertical axis,output of good X is measured on the horizontal axis,MPL is the marginal product of labor with a subscript indicating which good,P is the price of a good,and w is the wage rate.

A) -MPL_Y/MPL_X;-P_X/P_Y
B) -P_X/P_Y;-MPL_Y/MPL_X;
C) -P_X/w;-P_Y/w
D) -MPL_Y/w;-MPL_F/w
E) -MPL_X/MPL_Y;-P_X/P_Y