The normal force, is the reaction force that acts in the opposite direction to the weight, and that in a horizontal plane, is exactly this (following the principles of Newton's third law)
Therefore, from the mathematical definition of Weight we have that the normal Force is equivalent to
N = mg
Where,
m = mass
g = Gravitational acceleration
Our mass is 390Kg and acceleration, the product of gravity is equivalent to
![9.8m/s^2](https://img.qammunity.org/2020/formulas/physics/high-school/serhnh5eiqbsyqt1ft67qqsl3ye0y6szut.png)
Therefore the normal Force would be
![N = 390*9.8](https://img.qammunity.org/2020/formulas/physics/college/je2u5ka0rlgfnx755u0ywiqm6z0ujg1i8q.png)
![N = 3822N](https://img.qammunity.org/2020/formulas/physics/college/5pjjd38i4f5bbsg4865jzduinii9jeestq.png)