"Inapacketvoicecommunicationssystem,asource $!$ transmits packets containing digitized speech to a receiver. Because transmission errors occasionally occur, an acknowledgment $($ACK$)$ or a nonacknowl$-$ edgment $($NAK$)$ is transmitted back to the source to indicate the status of each received packet. When the transmitter gets a NAK, the packet is retrans$-$ mitted. Voice packets are delay sensitive and a packet can be transmitted a maximum of d times. If a packet transmission is an independent Bernoulli trial with success probability p$,$ what is the PMF of

T $,$ the number of times a packet is transmitted?"