Explain, dont just give answers

The following questions use the flow diagram below, where each packet has D bits, the line rate is R, and the propagation delay each way is P. (a) What is the correct latency equation for the transmissions shown? 3D A. L = +2P R 2D B. L= + 2P R +3P 3D C. L= R (b) What is the correct throughput equation if all packets contain data? 2D AT= I L B. T = 3D 3D C. T = L L D. T = 2D