Answer
$3.6 N$
Work Step by Step
Since all the masses experience same force, so whether we calculate for single mass or for all masses our result will be same.
Force experienced by an object is given as
$F =ma$
for $200 g(0.2kg)$ mass we have $ a=18m/s^2$
Thus $F = 0.2*18 N \\ F = 3.6 N$
