two classmates have decided to read all the volumes in a popular series of books. Katie has already read 4 volumes and will continue to read new ones at the rate of 1 volume per week. Maria, who hasn't started reading the series yet, will read 3 volumes per week. At some point, Marina will catch up with Katie and they will be reading the same book. How long will that take? How many volumes will each girl have read by then?