60. A refinery mixes high-octane and low-octane fuels to produce regular and premium gasolines. The profits per gallon on the two gasolines are $0.30 and $0.40, respectively. One gallon of premium gasoline is produced by mixing 0.5 gal of each of the fuels. One gallon of regular gasoline is produced by mixing 0. 25 gal of high octane with 0.75 gal of low octane. If there are 500 gal of high octane and 600 gal of low octane available, how many gallons of each gasoline should the refinery make? How, if at all, do the maximum profit and optimal production policy change if the refinery is required to produce at least 100 gal of each gasoline?