( 1)y = 30x+50(6-x)+40( 10-x)+80[8-(6-x0]

The relationship between total freight y and x is y=20x+860.

(2)y≤900

∴20x+860≤900

∴x≤2

∴x=0 or 1 or 2, * * * There are three transportation schemes.

(3) The lowest freight plan is: transfer 0 agricultural vehicles from warehouse B to county A and 6 agricultural vehicles to county B; 10 agricultural vehicles were transferred from warehouse a to county a, and 2 agricultural vehicles were transferred to county B.

The lowest freight y=50×6+40× 10+80×2.

∴y=860

Answer: The lowest freight is 860 yuan.

Please refer to question 27:

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