The serial number on a bill consists of a letter followed by eight digits and then a letter. How many serial numbers are possible, giving the following conditions (a) letters and digits cannot be repeated (b) letters and digits can be repeated (c) the letters are nonrepeated consonants and the digits can be repeated ( let y be a consonant)

Twelve different video games showing substance use were observed and the duration times of game play (in seconds) are listed below. the design of the study justifies the assumption that the sample can be treated as a simple random sample. use the data to construct a 99% confidence interval estimate of μ, the mean duration of game play. 4028 4316 4816 4650 4036 5010 4833 4331 4307