This part has been deleted from the exam. (b) (9) Computer A sends each message to computer B simultaneously over two not so reliable commu- nication links. Computer B can detect when errors occurred in a message. Let q denote the probability of a message transmission error on line 1. Also assume q is the message transmission error probability on line 2. A correct copy is considered to be received by Computer B if a correct copy is received on either line. Computer B requests retransmissions until it receives an error-free message. Let N be the number of transmissions required. (Count a transmission of a message over both lines as one transmission). (i) Find the PMF of N. The time to transmit a message from A to B is exponentially distributed with parameter u. If Computer B receives an error-free message, it sends a ACK (acknowledgement) back to A. If Computer B receives messages with errors on both lines, it sends a NAK (negative acknowledgement) back to A. The time to send an ACK or NAK back to A is also exponentially distributed with parameter u. Let X be the time it takes A to transmit an error-free message to B plus receive an ACK. (ii) Find the conditional PDF for X, given that N = 3. (iii) Find the PDF for X. This part has been deleted from the exam. (b) (9) Computer A sends each message to computer B simultaneously over two not so reliable commu- nication links. Computer B can detect when errors occurred in a message. Let q denote the probability of a message transmission error on line 1. Also assume q is the message transmission error probability on line 2. A correct copy is considered to be received by Computer B if a correct copy is received on either line. Computer B requests retransmissions until it receives an error-free message. Let N be the number of transmissions required. (Count a transmission of a message over both lines as one transmission). (i) Find the PMF of N. The time to transmit a message from A to B is exponentially distributed with parameter u. If Computer B receives an error-free message, it sends a ACK (acknowledgement) back to A. If Computer B receives messages with errors on both lines, it sends a NAK (negative acknowledgement) back to A. The time to send an ACK or NAK back to A is also exponentially distributed with parameter u. Let X be the time it takes A to transmit an error-free message to B plus receive an ACK. (ii) Find the conditional PDF for X, given that N = 3. (iii) Find the PDF for X