$(10$ pts$)$ Consider the figure below, which plots the evolution of TCP$\text{'}$s congestion window at the beginning of each time unit. In this abstract model $($NOT TCP Reno or Tahoe$),$ TCP sends a "flight" of packets of size cwnd at the beginning of each time unit.

The result of sending packets is that either $($i$)$ all packets are ACKed at the end of the time unit; $($ii$)$ there is a timeout for the first packet; $($iii$)$ there is a triple duplicate ACK for the first packet.

The initial value of cwnd is $1$ and the initial value of ssthresh is $8.$

$45$

Time unit $($in RTT$)$

Given evolution of TCP$\text{'}$s congestion window, provide following:

a$.$ List the times, at which TCP is in slow start, congestion avoidance and fast recovery states.

b$.$ List the times, at which the first packet in the sent flight of packets is lost and indicate whether the packet loss is detected via timeout, or by triple duplicate ACKs.

c$.$ List the times at which the value of ssthresh changes and provide the new value of ssthresh.