Comparing two averages of independent normal variables

Let $X_1,X_2,X_3,X_4,X_5$ be independent random variables with $X_1\sim N(200,8)$, $X_2\sim N(104,8)$, $X_3\sim N(108,15)$, $X_4\sim N(120,15)$ and $X_5\sim N(210,15)$. Let $U=\frac{X_1+X_2}2$ and $V=\frac{X_3+X_4+X_5}3$. Then $P(U>V)$ equals __________________