From Mechanics

In the vertical direction the forces on the tank must be in equilibrium.

\displaystyle \uparrow \ -mg+N+5000\cos {{65}^{\circ }}=0

or

\displaystyle \begin{align} & N=mg-5000\cos {{65}^{\circ }}=500\times 9.8-5000\times 0.423 \\ & =4900-2113=2787\ \text{N} \\ \end{align}