If the mean of the following frequency distribution is `62.8` and the sum of all the frequencies is `50`, then compute the missing frequency `x` and `y`.

Class	Frequency
0`-`20	`5`
20`-`40	`x+y`
40`-`60	`10`
60`-`80	`y-x`
80`-`100	`7`
100`-`120	`8`