we know that
A simple formula for the area of a rhombus when you know the lengths of the diagonals is half the product of the diagonals
Area=d1*d2/2
d1=500 yd
d2=800 yd
1 mile is equal to -----> 1760 yd
x mile---------------> 500 yd
x=500/1760----> x=0.2841 mi
1 mile is equal to -----> 1760 yd
x mile---------------> 800 yd
x=800/1760----> x=0.4545 mi
Area=(0.2641*0.4545)/2-----> 0.06 miles²
the answer is
0.06 miles²