mohon bantuannya yah !!!

a = F / (m₁ + m₂)
   = 30 N / (2 kg + 3 kg) = 6 m/s²

F kontak = m₂ a
               = (3 kg)(6 m/s²) = 18 N
atau
F kontak = F - m₁ a
= 30 N - (2 kg)(6 m/s²) = 18 N
Jawaban: A.