An acre is 43,560 ft² because the customary system hates you.
Let's find out how many square feet the parcel is so we can convert it into acres.
The area of a rectangle is its base times its height.
A = bh
A = 234 ft * 878 ft
A = 205,452 ft²
Divide by 43,560.
A ≈ 4.7165 acres. (round as needed)
