$1.$ Consider a $10$ Mbps shared Ethernet with Bus Topology. The total length of the cable is $2000$m and the propagation speed is $2\backslash$times $10^8$m $/$ s$.$ Station A$,$ on one side of the bus, starts sending a long frame at t$\_1=0.$ Station C$,$ on the other side of the Bus starts sending a long frame at time t$\_2=3\backslash$mu sec$.$ The size of the frame is long enough to guarantee the detection of collision by both stations. Find: a$.$ The time when station C detects the collision, t$.$ b$.$ The time when station A detects the collision, t$.$ c$.$ The number of bits station A has sent before detecting the collision. d$.$ The number of bits stations C has sent before detecting the collision