We are given a bit transmission facility that transmits each bit correctly with probability (1 - BER) and incorrectly with probability BER, where BER = 10-6. The bit errors are independent. We send bits in groups of 7, and we add a parity bit so that the groups of 8 bits that we send always contain an even number of 1's. What is the probability that the group of 8 bits arrives with transmission errors not detected by the parity bit?