The ratio of 40K to 40Ar was used to date moon rocks returned by the Apollo 11 flight. Potassium-40 decays to argon-40 by positron emission with a half-life of 1.3 billion years. Assuming no 40 Ar was present initially and that none escaped, how old is a rock that has a K-40 to Ar-40 ratio of 0.143? x 10 (select) year