Answer:
161.7N
Explanation:
Given parameters:
Mass of the box  = 55kg
Coefficient of friction  = 0.3
Applied force  = 140N
Unknown:
Frictional force on the box = ?
Solution:
The frictional force on the box is a force that opposes the motion of the box.
To find the value of this force;
    Fr  = u m g
u is the coefficient of static friction
m is the mass
g is the acceleration due to gravity
 So;
   Fr  = 0.3 x 55 x 9.8  = 161.7N