Gavin and his good buddy Vincent are both mechanics at a shop that does oil changes. They are in a friendly competition to see who can complete the most oil changes in one day. Gavin has already finished 7 oil changes today, and can complete more at a rate of 2 oil changes per hour. Vincent just came on shift, and can finish 3 oil changes every hour. Sometime during the day, the friends will be tied, with the same number of oil changes completed. How many oil changes will Gavin and Vincent each have done? How long will that take?