A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered.If the area of the field is 800 sq.ft, how many feet of fencing will be required ?  Choose the correct choice from the following options.
A) 100 feet
B) 120 feet
C) 150 feet
D) 180 feet
E) 186 feet

Rationale: "explanation : we are given with length and area , so we can find the breadth . as length * breadth = area = > 20 * breadth = 800 = > breadth = 40 feet area to be fenced = 2 b + l = 2 * 40 + 20 = 100 feet answer : option a"
Answer: A