Question: How many Grand Slam singles championships were won by the winner of the 1974 Virginia Slims of Newport?
Sentence (from "1974 Virginia Slims of Newport"): The 1974 Virginia Slims of Newport, was a women's tennis tournament played on outdoor grass courts at the Newport Casino in Newport, Rhode Island in the United States that was part of the 1974 Virginia Slims World Championship Series.
Relevant evidence: Yes