You have a mass of 54 kg and are sitting on a stool. the normal force the stool applies on you is

529.2 N

Explanation:

As we have studied the first law of motion, which states that every action has some reaction, equal in magnitude but having an opposite direction.

The force that is acting on the student will be due to gravitational force, that is equal to his weight.

                                              F=mg: 54kg x 9.8m/s^2 =529.2 N

So the weight of student is exerting downwards towards the stool and land. The stool will also exert a force on the student that will be equal in magnitude but opposite in direction, then it will be 529.2 N.

This is because the student is sitting in a constant state and all the weight is exerted on the stool.

Note: This answer is very generic supposing that all the weight of the student is on stool. But, if we suppose that student's legs are on floor so it means the force of gravity acting on the stool has become less because student's mass on stool is less. So the answer would be a force somehow less than 529.2 N.  However, since the question asked normal force, it would be weight of student in general terms.

Hope it helps!