A cistern 7m long and 4 m wide contains water up to a depth of 1 m 25 cm. The total area of the wet surface is: Choose one:
A) 49 m 2
B) 50 m 2
C) 53.5 m 2
D) 55.5 m 2
E) 57 m 2

Rationale: "area of the wet surface = [ 2 ( lb + bh + lh ) - lb ] = 2 ( bh + lh ) + lb = [ 2 ( 4 x 1.25 + 7 x 1.25 ) + 7 x 4 ] m 2 = 55.5 m 2 . answer : option d"
Answer: D