$\begin {array} {1 1} (a)\;\large\frac{R_X}{R_Y} & \quad (b)\;\bigg( \large\frac{R_X}{R_Y}\bigg)^2 \\ (c)\;\large\frac{R_Y}{R_X} & \quad (d)\;\bigg( \large\frac{R_X}{R_Y}\bigg)^{\large\frac{1}{2}} \end {array}$