### Three Boxes

Three boxes sit next to each other on a flat table. Their masses are:
$m_{1}=45.2 kg$., $m_{2}=22.8 kg$. and $m_{3}=34.3kg$.

a) What horizontal force F is needed to push the boxes to the right,
as one unit, with acceleration of $1.32 m/s^{2}$?

b) Find the force exerted by $m_{2}$ on $m_{3}$.

c) Find the force exerted by $m_{1}$ on $m_{2}$.