A school plans to use no more than 1900 science and technology books and no more than 1620 personal literature books. .....

Set x medium-sized book corners and 30-X small book corners.

80X+30(30-X)≤ 1900

50X+60(30-X)≤ 1620

80X+900-30X≤ 1900

50X≤ 1000

X≤200

50X+ 1800-6X≤ 1620

180≤ 10X

18≤X

18≤X≤20

The value of x can be 18,19,20, and there are three construction schemes:

When X= 18, 30-X= 12.

When X= 19, 30-X= 1 1.

When X=20, 30-X= 10.

Scheme 1: Set 18 middle corner and 12 small corner.

Scheme 2: Set 19 medium book corner and 1 1 small book corner.

Scheme 3: Set 20 medium-sized corners and 10 small corners.

① the cost of scheme 1: 860x18+570x12 = 22320.

② Cost of Scheme II: 860x19+570x11= 22610.

③ Cost of Scheme III: 860x20+570x 10=22900.

Option 1 has the lowest cost, with the lowest cost of 22,320 yuan.

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