[P_Y(y) = \left{ \begin{array}{ll} \frac{2}{7} & \text{for } y = 4.5, 2, 0.5 \ \frac{1}{7} & \text{for } y = 0 \ 0 & \text{otherwise} \end{array} ight.] pmf represent..dont wirte this type ..give complet mathematical writings