Can Acadian take advantage of the quantity discount, and if so when?

Acadian Bakers is a small sweets bakery in Houston, Texas. One of its products is a croissant. Acadian buys frozen croissants and bakes them. For the sake of quality, the company doesn't want to store its frozen goods for more than one week. For orders of more than 576 cases, the delivery is free (saving $15 per order). A case contains 144 frozen croissants. Acadian has collected its total weekly sales for croissants (in cases) for the last 10 weeks. Management believes that the sales of croissants are increasing.
Week                        Sales
1 ............................    461
2 ............................    450
3 ............................    463
4 ............................    458
5 ............................    476
6 ............................    492
7 ............................    482
8 ............................    491
9 ............................    488
10 ..........................    488