Please help explain for better understanding.

In 2004, Stephanie entered into a contract with Laura for the design and installation of custom-crafted window treatments. The window treatments were constructed of chemically infused wormwood and came with an express guarantee to keep a minimum of 99 percent of sunlight out of the home for ten years. Before entering into the contract, Laura told Stephanie that she had just recently developed the treated wormwood and had yet to form a corporation, however, her new company would be called "Wormwood Windows, Inc." Laura signed the contract "Laura, for Wormwood Windows, Inc.," and Stephanie paid the agreed-upon price of $50,000 with a check made out to the corporation. Two months later the corporation filings were approved by the state, and Laura deposited the $50,000 into her business account. In 2009, Stephanie noticed that the wormwood window treatments began to crack internally and outside light began to seep through the treatments into her home. Stephanie contacted Laura about the problem and demanded that Laura make good on her guarantee. Laura insists that there is no guarantee because the contract was entered into before the formation of the corporation. What should Stephanie say to Laura about the liability of both Wormwood and Laura?