In a wireless sensor network link protocol, a frame is retransmitted whenever it receives an error. The average number of frames transmitted per error$-$free reception $($Nr$)$ is $(1-$ FER$)\text{'},$ where FER is the frame error rate. If the overhead per frame is n bits, which is independent of the frame size $($N bits$),$ show that the average number of bits transmitted per error$-$ free reception of one bit of information is given by: N $+$n N$(1-$ P$.)$N$+$n where Pe is the bit error probability of the link.