Each day, QBlitz, a Seattle-based startup, offers a single product through its website. The product is available for order only on one day, and no other products are available during that day. To add to this odd selling strategy, QBlitz does not post prices for its products. Instead, for each product there is a reserve price. On the day a product is available, customers can submit bids. All of the bids that exceed the reserve price are told at the end of the day that they “won” the product and they pay the price they bid. QBlitz then adds up all of the winning bids and submits an order to a supplier for the needed quantity. If the supplier delivers that quantity, then QBlitz ships the product to the winners once the product is received. However, if the supplier delivers only a portion of the ordered quantity, then QBlitz ships the product to the highest bidders that it can satisfy and notifies the others that they will receive a refund because they will not in fact receive the product. The QBlitz system is best described as 

a. Make-to-stock. 

b. Make-to-order. 

c. Assemble-to-order. 

d. Mass customization.