Problem: To make a case of cookies, Walker Shortbread Company uses 10 pounds of butter, 20 pounds of flour, 5 pounds of sugar, and 10 ounces of salt. Currently, butter costs $1.50/lb, flour costs 25¢/lb, sugar costs 50¢/lb and salt costs 80¢/lb (or 5¢ per ounce).
Which input demand is most elastic, and which is least elastic?