Suppose that three high-tech factories each produce X pieces, and the other 28 factories each produce Y pieces.

85/25=3.4

Then the remaining 28 factories produce 1 piece and the three high-tech factories produce 3.4 pieces.

3.4y+28y=640

y= 16.9

Because the number of pieces produced should be an integer, and X and Y are the number of pieces produced by the factory that produces the most of the two factories.

In the first case, when y= 17, 17*85= 1445 (minutes) is required.

X=55 takes 55*25= 1375 (minutes).

If the time is long, it can be seen that it takes 1445 points to produce 640 pieces.

In the second case, y= 16 needs 16*85= 1360 (minutes).

X=64 takes 64*25= 1600 (minutes).

If the time is long, it can be seen that it takes 1600 points to produce 640 pieces.

So choose the first case.

Two of the three high-tech factories produce 55 pieces and one produces 54 pieces. *** 164 pieces

The remaining 28 factories each produce 17 pieces. ***476 yuan.