Solving a problem in physics section 70 point 72 electr

72. Between the plates of a flat capacitor with an area of S = 50 cm2, charged to the potential difference U = 500 V, there is a porcelain layer (ε = 5). Determine the surface density σ of the charge on the plates of the capacitor and its electric intensity if the field strength in the capacitor is E = 400 V / cm.