Give the mathematical expression for the total packet delay, as a function of Pd, L, R1, R2, R3, d1, d2, d3 and s. Show your calculations. Use the expression to come up with a numeric answer when: L = 10000 bits, Pd = 0.5 msec, R1 = 1 Gbps, R2 = 2 Mbps, R3 = 10 Mbps, d1 = 5 km, d2 = 10 km, d3 = 10 km, s = 2.5 x 10 8 m/sec.