If p1 and P2 are effective lateral loadings at the bottom and top exerted by a level earth subjected to a super-load on the vertical face of height h of a retaining wall, the horizontal pressure p per unit length of the wall, is____________________?

• A. [( – )/2] h
• B. [( + )/4] h
• C. [( + )/2] h
• D. ( – h