A parallel-plate capacitor has plate area 40 cm². The dielectric has two layers with permittivity ε₁ = 4ε_o and ε₂ = 6ε_o, and each layer is 2 mm thick. If the capacitor is connecte  to a voltage 12 V, calculate: 

(a) The capacitance of the capacitor, 

(b) The total charge on each plate, 

(c) The values of E, D, and P.