Network A has MTU of 1500 bytes
Network B has MTU of 620 bytes
we have to find the size of packets that is received at network C
Here is the thing , i think the data sent is 1380 , that is .. it does not include the header .
therefore we have the data as 1380 B.
now it will have no problem in network A .
but for network B , MTU = 600+20
thus , the data is broken into three segments .. (600+20) + (600+20)+(180+20)
thus the total data received will be 1440 B .
PS
made easy solution doesn't make much sense .. i think 1380 is the total data that station -1 is sending , otherwise they would have explicitly mentioned that it contains 20 B header , like they did for MTU of networks .