Question: Using Benford's law According to Benford's law, the probability that the first digit of the amount of a randomly chosen invoice is an 8 or a 9 is 0.097. Suppose you examine randomly selected invoices from a vendor until you find one whose amount begins with an 8 or a 9.

(a) How many invoices do you expect to examine until you get one that begins with an 8 or 9? Justify your answer.

(b) In fact, you don't get an amount starting with an 8 or 9 until the 40th invoice. Do you suspect that the invoice amounts are not genuine? Compute an appropriate probability to support your answer.