A student is either pushing or pulling a 50 kg box along a carpeted platform. However, the box remains at rest, even though the student tests a number of different setups. What can be inferred about the forces acting on the box?
a) The force exerted is equal to the force of friction.
b) The net force acting on the box is zero.
c) The force exerted is greater than the force of friction.
d) The force exerted is less than the force of friction.