Evgenia is a resident of California. She recently purchased two computers from an online retailer that did not charge California sales tax. The retailer happened to be offering a steep discount if two computers were purchased in a single transaction. She gave one of the computers to her sister (also a California resident) for her birthday a few days after the computers arrived. Because Evgenia already had a fully functional com-puter, she stored the other computer for the next 18 months before finally upgrading to a new one. Is Evgenia responsible for California use tax for one, both, or neither computer, and when is the use tax due?