According to the meaning, 80x130 (30-x) ≤1900, 50x160 (30-x) ≤1620.
The solution of this inequality group is 18≤x≤20.
Because x can only be an integer,
The value of ∴x is 18 or 19 or 20.
When x= 18, 30-x =12;
When x= 19, 30-x =11;
When x= 20, 30-x= 10.
Therefore, there are three formation schemes:
Scheme 1: Set 18 middle corner and 12 small corner;
Scheme 2: Set 19 middle book corner and 1 1 small book corner;
Scheme 3: Set 20 medium-sized corners and 10 small corners.
(2) Method 1: Since the cost of setting middle-sized book corners is greater than that of setting small-sized book corners, the less the number of middle-sized book corners, the lower the cost.
Therefore, the cost of the first scheme is lower. The lowest cost is 860× 18,1570×12 = 22,320 (yuan).
Method 2: ① The usage of Scheme 1 is: 860× L810 570×12 = 22 320 (yuan);
② The usage of the second scheme is: 860×19×11= 22610 (yuan).
③ The application method of Scheme III is: 860×20+570× 10 =22 900 yuan.
Therefore, Option 1 has the lowest cost, with the lowest cost of 22 320 yuan.