Answer:
30.256 N
Step-by-step explanation:
m = 24 kg 
M = 62 kg 
F = 42 N
Le a be the acceleration in the system and f be the contact force between both the blocks. 
Use Newton's second law
F - f = m a ..... (1)
f = M a .... (2) 
Adding both the equations 
F = (m + M) a
42 = (62 + 24) a 
a = 0.488 m/s^2 
Put the value of a in equation (2), we get 
f = 62 x 0.488 = 30.256 N