The tip of an atomic force microscope $($AFM$)$ is subjected to the forces shown

$($if you are curious, see the description in Prob. $4\mathrm{.}5$ on p$.215$ of what an AFM is

used for$).$ Use a vector approach to determine

$($a$)$ an equivalent force system at point $B,$

$($b$)$ an equivalent force system at point $O.$