Note: This is a computer networks question. please slove( help me with all parts) thanks

Consider the figure below. Suppose Host A has a packet of size S=1500B to send to Host B at time t=0. Let B_1=10 Mbps, B_2 = 20 Mbps, and B_3 = 30 Mbps be the bandwidth capacities of the three links respectively. Let D_1, D_ 2 and D_3 be the corresponding lengths of the three fiber links and let V denote the speed of light. Assume that processing and queuing delays are negligible and answer the following questions in terms of the variable names. At what time T_1. does the packet leave R_1? The packet is said to leave a router when it has been fully transmitted on to the next link. At what time T_2 does the packet leave R_2? At what time T_3 does the packet reach host B? Now suppose Host A has a second packet, also of size S, to be sent to Host B and sends the two packets back to back. At what time T_4 does the second packet reach R_1