The amount of sugar transported to place A is not less than 1 15 tons, so the solution of15x+10 (10-x) ≥115 is x≥3.
In addition, 240 tons of sugar will be transported, so15 (x+y)+10 (10-x+10-y) = 240.
Simplified to x+y=8, that is, y = 8-X.
Total freight m = 630x+420 (10-x)+750y+550 (10-y).
=2 10x+200y+9700
Substitute y=8-x to get m =10x+11300.
And x≥3, when x=3, m takes the minimum value. m = 10 * 3+ 1 1300 = 1 1330
Therefore, three big trucks and seven small trucks are arranged to go to A, and five big trucks and five small trucks are arranged to go to B, with the least freight.
At least 1 1330 yuan.