A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered. If the area of the field is 720 sq. feet, how many feet of fencing will be required?	Choose the correct option
A) 34
B) 92
C) 68
D) 88
E) none

Rationale: "explanation we have : l = 20 ft and lb = 720 sq . ft . so , b = 36 ft . length of fencing = ( l + 2 b ) = ( 20 + 72 ) ft = 92 ft . answer b"
Answer: B