$2\mathrm{.}137$ The foree vector $F$ points along the straight line from point

A to point $B.$ Its magnitude is $|F|=20N.$ The coordinates of

points A and $B$ are $x_A=6m,y_A=8m,z_A=4m$ and $x_B=8m,$

$y_B=1m,z_B=-2m$

$($a$)$ Express the vector $F$ in terms of its components.

$($b$)$ Use Eq$.(2\mathrm{.}34)$ to determine the cross products $r_{A}F$ and

$r_{B}F.$

Problem $2\mathrm{.}137$