Two part force question

Question

Blocks with masses of 6.0 kg, 7.0 kg, and 9.0 kg are lined up in a row on a frictionless table. All three are pushed forward by a 12 Newtons force applied to the 6.0 kg block.

How much force does the 7.0 kg block exert on the 9.0 kg block?

How much force does the 7.0 kg block exert on the 6.0 kg block?

Answers in two significant figures

Answer 1

F = m * a

F = 12 N

m = 6 kg + 7 kg + 9 kg

a = ?

a = F / m = 12 / ( 6+7+9) =  12 / 22 = 0.545 m/s/s

Force of 6 kg block = 6 *12 / 22 = 3.272 N

Force  of 7 kg block = 7 *12 / 22 = 3.818 N

Force  of  9 kg block = 9 *12 / 22 = 4.909 N