How much water is added in cement mortar to determine compressive strength of cement?
a) Equal to (P/4 + 3) percent of total mass of cement and sand, where P is water required for standard consistency
b) 0.4 times the mass of cement
c) Equal to 0.85P percent of total mass of cement and sand, where P is water required for standard consistency
d) 0.28 times the mass of cement mortar