Problem $4$: $(30$ points$)$ At the shown instant $=30.$

$V_B$ is horizontally to the right.

$a_B$ is in the direction of the $r($that is $=30).$

$V_A=300\frac{m}{s}$ horizontally to the right

$a_A=6\frac{m}{s}$ horizontally to the right

Determine the ${}^{}$ and tilde$(r),$ when the radar of

Plane A locks onto plane $B.$