$1.$ Calculate the total time required to transfer a $1000-$kB file in the following cases, assuming an RTT of $100$ ms$,$ a packet size of $1$ kB data, and an initial $2\backslash$times RTT of $$handshaking$$ before data are sent. $($a$)$ The bandwidth is $1\mathrm{.}5$ Mbps$,$ and data packets can be sent continuously. $($b$)$ The bandwidth is $1\mathrm{.}5$ Mbps$,$ but after we finish sending each data packet, we must wait one RTT before sending the next. $($c$)$ The bandwidth is $$infinite$,$ meaning that we take transmit time to be zero, and up to $20$ packets can be sent per RTT$.($d$)$ The bandwidth is infinite, and during the first RTT$,$ we can send one packet $(211),$ during the second RTT we can send two packets $(221),$ during the third we can send four $(231),$ and so on$.$