Then->; D is 200-X,

Because the cost of transporting two villages to warehouse C is relatively low, warehouse C must be full in order to make the freight lowest.

Then b->; The transportation volume of c is 260-X,

Then b->; D is 300-(260-x) = 40+x.

So the freight of A is 20*X+25*(200-X)=5000-5X.

The cost of b is15 * (260-x)+18 * (40+x) = 3x+4620.

B-A=8X-380

X is an integer from 0 to 200, 8X-380 & gt；; 0，X & gt47.5,

Therefore, when x takes 0 to 47, the freight of B is greater than that of A,

When x takes 48 to 200, the freight of A is greater than that of B.

(2)

B freight 3x+4620

When the sum of the two villages' freight is 9620-2X and X=70, the sum of the two villages' freight is the least, which is 9620-2*70=9480 yuan.