Savings to buy a computer

Dave took Mary out for a romantic dinner where conversation turned to the subject of marriage.
Dave had been saving for an engagement ring, but he was in graduate school and in dire need of a new computer.
Mary was understanding, telling Dave they had the rest of their lives to get engaged, so he should use his savings to buy a computer instead.
During dessert, Dave suddenly reached into his pocket and pulled out an engagement ring.
Mary was stunned, but after she collected herself, she looked up and prompted: "Well, don't you have something to ask me?"
Dave then got down on bended knee. "Honey," he said, "Will you buy me a new computer?"