Let the purchase price of the commodity be a and b be the quantity of the commodity without discount.

1000 * A = 100 * A * 125% * 90%+( 1000- 100-B)* A * 125% * 40%

1000 = 1 12.5+500-50-B * 0.5

B=875

At least 875 items without discount can be sold without loss.