A masonry dam (density = 20,000 N/m3
) 6 m high, one metre wide at the top and 4 m wide at the
base, has vertical water face. The minimum stress at the base of the dam when the reservoir is
full, will be
(A) 75 N/m2
(B) 750 N/m2
(C) 7500 N/m2
(D) 75000 N/m