Please, answer the following questions: Each calculated expression and a brief description of each element in the calculation are needed. Solutions limited to final numerical values will not be considered correct. a) [10 pts] There are three packet switches between two hosts, the first link has a rate of R1 = 2 Mbps, the second link has a rate of R2 = 1 Mbps, and the third and fourth links have rates R3 = 3 Mbps and R4 = 4Mbps respectively (R2