two mining fields, field a and field b, of a coal mining company produce lignite and bituminous coal. the operating cost per day for field a and field b are $55,000 and $45,000, respectively. the recent records at the company indicate that field a can produce 250 tons of lignite along with 300 tons of bituminous coal per day, whereas field b can produce 200 tons of lignite along with 450 tons of bituminous coal per day. the expected demands to be met are 120,000 tons of lignite and 170,000 tons of bituminous coal. to minimize the operating costs of the mining fields, how many days does the company need to operate each of these fields?
