Assume the five layer network protocol stack as above with two routers in between source and destination. Explain how data travels from source to destination using the Internet Protocol Stack and the two routers. As message M travels through the protocol stack, it is modified due to addition and deletion of headers in each layer. When a message travels from source to destination through two routers, how many times the message M is modified before it reaches to the destination as M. Show your work to determine this number.