The average of 17 numbers is 55. The average of the first 6 numbers is 49.5 and that of the next 8 numbers is 60.5. The 16th number is 4 less than the 15th number and 6 less than the 17th number. What is the average of the 15th and 17th numbers?
1
48
2
46
3
41
4
53