As of April 2006, roughly 50 million web domain names were registered (e. g., ). (a) How many domain names consisting of just two letters in sequence can be formed? 676 Correct: Your answer is correct. seenKey 676 domain names How many domain names of length two are there if digits as well as letters are permitted as characters? [Note: A character length of three or more is now mandated.] 1296 Correct: Your answer is correct. seenKey 1,296 domain names (b) How many domain names are there consisting of three letters in sequence? [Note: All are currently taken.] 17576 Correct: Your answer is correct. seenKey 17,576 domain names How many of this length are there if either letters or digits are permitted? 46656 Correct: Your answer is correct. seenKey 46,656 domain names (c) How many domain names are there consisting of four letters in sequence? 456976 Correct: Your answer is correct. seenKey 456,976 domain names How many of this length are there if either letters or digits are permitted? 1679616 Correct: Your answer is correct. seenKey 1,679,616 domain names (d) As of a certain date, 97,397 of the four-character sequences using either letters or digits had not yet been claimed. If a four-character name is randomly selected on that date, what is the probability that it is already owned? (Round your answer to four decimal places.) .942 Correct: Your answer is correct. seenKey 0.9420