x = 0； 26 vehicles, 10 seats; Cost =260×6×0.7= 1092 yuan;

x = 1； 10 seat, 2 1 vehicle; Cost = 210× 6× 0.7+50× 5× 0.8 = 882+200 =1082 yuan;

x = 2； 10 seats 16 vehicles; Cost =160× 6× 0.7+100× 5× 0.8 = 672+400 =1072 yuan;

x = 3； 10 seat 1 1 vehicle; Cost =110× 6× 0.7+150× 5× 0.8 = 462+600 =1062 yuan;

x = 4； 6 vehicles 10 seats; Cost = 60× 6× 0.7+200× 5× 0.8 = 252+800 =1052 yuan;

x = 5； 10 seat 1 vehicle; Cost =10× 6× 0.7+250× 5× 0.8 = 42+1000 =1042 yuan;

x = 6； 0 vehicles 10 seats; Cost = 200× 5× 0.8+10× 5 =1000+50 =1050 yuan;

Therefore, there are five buses with 50 passengers, and the bus with 10 passengers has 1 vehicle, which is the most cost-effective, and the cost is = 1042 yuan;

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