The average of fifteen numbers is 60. The average of the first seven numbers is 63 and the average of next five numbers is 59. The last number is half of the 13^th number and the 14^th number is four more than the last number. Which of the following is/are correct?

I. Average of the last three numbers is an integer

II. Fourteenth number is divisible by 11

III. Average of 13^th and 15^th number is not 65