6x+5(40 times) ≥220

4x+5(40-x)≥ 178

∴ 20 ≤ x ≤ 22: x is an integer ∴ x = 20,21,22.

① A: 20 B: 20

②A:2 1 B: 19

③ A: Twentytwo B: 18

(2) Let the total freight be Y yuan.

Y= 190x+200(40-x)

=- 10x+8000

∫k < 0 20≤x≤22

∴x↑_Y↓

When x=22, y is minimum =7780.