Area of trapezoid is given by Area=1/2(a+b)*h but the scale is: 1/2in=40 ft hence 1 in=80 ft the dimensions of the trapezium is: Base=80*3.5=280 ft Base=80*5=400 ft Height=80*4=320 ft thus the area is: A=1/2(280+400)*320 A=108,800 but 1 acre=43560 ft² Thus: 108800 ft²=108800/435602.4977=~2.5 acres