Suppose that a sender and a receiver are using ARQ to perform reliable data delivery.

$($a$)$ In a Go$-$Back$-$N ARQ protocol, the window size is $8.$ Frames with sequence numbers $1,2,3,4,5$ and $6$ have been sent. The sender just received an ACK for frame $1$ and $2.$ Frames $7,8,9,10$ and $11$ are waiting to be sent. Draw the time diagram showing this scenario. $(2$ marks$)$