60. An acre, a unit of land measurement still in wide use, has a length of one furlong length of one furlong $\left(\frac{1}{8} \mathrm{mi}\right)$ and a width one-tenth of its length. (a) How many acres are in a square mile? (b) How many square feet are in an acre? See Appendix $E .$ (c) An acre-foot is the volume of water that would cover 1 acre of flat land to a depth of 1 foot. How many gallons are in 1 acre-foot?
