Consider the transfer of a file containing $1\mathrm{.}5$ million $8-$bit characters from one station to another. What is the total elapsed time for the following cases?

A circuit$-$switched, star$-$topology LAN. Call setup time is negligible and data rate on the medium is $64kbps.[$A$]$ seconds

A Datagram, Bus Topology LAN with two stations $1km$ apart. Data rate $1Mbps,$ and a frame size $256$ bits $($includes $56$ bits overhead$).$ Each frame is

acknowledged with $88$ bits frame before the next is sent. The propagation speed on the bus is $200\frac{m}{u}s.$ No processing delay. $[$B$]$ seconds