12x+10 (10-x) ≤105, the solution is x ≤ 2.5.
∵x is a non-negative integer, ∴x can be 0, 1, 2.
There are three purchase schemes: 0 sets of type A and 0 sets of type B 10;
Type a 1, type b 9;
2 sets of type A and 8 sets of type B..
(2)240x+200( 10-x)≥2040，
The solution is x≥ 1, so x is 1 or 2.
When x= 1, the subscription fund is:12×1+10× 9 =102 (ten thousand yuan);
When x=2, the purchased capital is12× 2+10× 8 =104 (ten thousand yuan).
So in order to save money, we should buy 1 model A and 9 models B.
(3) In 10, the total amount of funds for enterprises to treat sewage by themselves is:
102+10×10 = 202 (ten thousand yuan),
If sewage is discharged to a sewage plant for treatment:
2040×12×10×10 = 2448000 (yuan) = 2448 (ten thousand yuan).
Savings: 244.8-202=42.8 (ten thousand yuan).