Final answer:
The person is exerting an equal force of 150 N against the crate, as per Newton's Third Law of Motion, meaning the force exerted by the person is equal to the normal force of 150 N.
Step-by-step explanation:
To determine how much force a person is currently exerting to lift a crate with a mass of 30 kg, given the normal force supplied by the floor is 150 N, we need to consider the equal and opposite force applied by the person. According to Newton's Third Law of Motion, if the normal force acting upward from the floor is 150 N, then the person must be exerting an equal amount of force in the opposite direction, which would also be 150 N in order to maintain static equilibrium (assuming no other vertical forces are acting on the system, such as acceleration or additional weights).