We use the stop and wait arq protocol between a sender and receiver. the transmission line that connects them has 50ms one-way propagation delay. taking all factors into account, the sender timeout is set to 140ms, and the system is working properly under these conditions. we observe now, however, that the channel has changed, and its one-way propagation delay has grown to 70ms. how much should be the new sender timeout, if there is no other change in the system? the timeout parameter should remain the same. the reason is that we consider a data link layer protocol, which does not have to deal with physical layer parameters, such as the propagation delay. due to 20ms increase in the propagation delay, the timeout should also increase with the same amount, since the other parameters, such as processing time, did not change. the new timeout parameter should be set to 180ms.