Consider the transfer of a file containing 1 million characters from one computer to another. Transfer consists of a sequence of cycles. For one cycle, a = (time for data frame + propagation) + (time for ACK frame + propagation). The throughput refers to the number of sequences required to transfer 1 million characters. Each character in its digital form requires 8 bits. The two computers are D = 1 km apart, and each generates a data rate of b = 1Mb/s, with a frame size s = 256 bits, which includes 80 bits of header. The propagation speed on the bus is 200 m/ sec. Find the total elapsed time using throughput for the following two cases: (a) A bus topology, with each frame acknowledged with an 88-bit frame before the next frame is sent. (b) A ring topology having a total circular length of 2D, with the two computers D distance apart. Acknowledgment is achieved by allowing a frame to circulate past the destination host back to the source host. The ring has N = 100 repeaters, each of which introduces a delay of 1 bit time. please with explai