All-Numeric Passwords. The technology consultancy Data-Genetics published the online document PIN analysis. In addition to analyzing PIN numbers, passwords trends were examined. Seven million all-numeric passwords were collected and yielded the following estimate of the probability distribution of the number of digits used in an all-numeric password.

Digits	Probability	Digits	Probability
4	0.492	9	0.029
5	0.092	10	0.015
6	0.178	11	0.004
7	0.073	12	0.003
8	0.113	13	0.001

On average, approximately how many digits would you expect an allnumeric password to have? Explain your answer.