A) a=xy is the total rectangular area of the two fields. The area of each field is ½xy. If the area of each field is maximised it will be square of side x, so the total area of the fields is a=2x².
B) 3x+y=1000 is total amount of fencing split between the parallel and perpendicular fences.
C) If the total area is maximised, it will be a square so x=y and 3x+x=1000, so x=y=1000/4=250 feet.
If the area of each field is maximised, y=2x so that each field is square, and 3x+2x=1000, so x=1000/5=200 feet. The perpendicular fences are 200 feet long are the parallel fence is 400 feet long. The combined area will be 80,000 square feet, in a rectangle which is 400 by 200 feet.