Total number of transmission = 54
1 2 3 4 5 6 7 8 9 6 7 8 9 10 11 8 9 10 11 12 13 10 11 12 13 14 15 12 13 14 15 16 17 14 15 16 17 18 19 16 17 18 19 20 18 19 20
(Bold numbers represent one window)
= 47
Also we need to send 7 dummy packet for 7 windows.
Therefore total = 47 + 7
= 54 transmissions.