Carla Windows manufactures and sells custom storm windows for three-season porches. Carla also provides installation service for the windows. The installation process does not involve changes in the windows, so this service can be performed by other vendors. Carla enters into the following contract on July 1, 2020, with a local homeowner. The customer purchases windows for a price of $2.420 and chooses Carla to do the installation. Carla charges the same price for the windows irrespective of whether it does the installation or not. The customer pays Carla $1,920 (which equals the standalone selling price of the windows, which have a cost of $1,100) upon delivery and the remaining balance upon installation of the windows. The windows are delivered on September 1, 2020. Carla completes installation on October 15, 2020, and the customer pays the balance due.