county's four recycling drop$-$off locations. The four drop$-$offs have characteristics as given in the table below.

Location

$x_{?}$ Y$-$

coordinate coordinate Tonnage

Drop$-$off

point A

$1$

$8$

$10$

Drop$-$off

point B

$6$

$7$

$35$

Drop$-$off

point C

$6$

$2$

$25$

Drop$-$off

point $D$

$4$

$7$

$50$

Determine the $x$ and $Y$ coordinates of centre of gravity of these four locations?