Basically 3 boxes, somehting like this; Masses are as followed: M1= 28 kg, M2= 18.7 kg, M3= 28.7 kg. The applied force on the box is 644 N Part A) What is the magnitude of the contact force between M1 and M2 Part B) What is the magnitude of the contact force between M2 and M3 To find the contace force between M1 and M2, i used this equation; 644/(28 + 18.7) for Part A, and 644/(18.7 + 28.7) for Part B. The anwers are; Part A, 13.79, and for Part B, 13.58. Is this the correct method? If not, what can be done to achieve the correct answer?