A teacher has four books-A, B, C, and D-to assign to four students in any order he prefers. Set S includes all possible arrangements of the four books.
Set X includes all possible arrangements when book C is chosen first and D is chosen second.
Which notation is correct?
If book C is chosen first and D is chosen second, in how many ways can the teacher assign the books?
с

Suppose "true-talent" average exit velocity (aev) on batted balls for all players is normally distributed with mean 86 mph and a standard deviation of 2 mph. for any sample of individual batted balls hit by one player, the standard deviation of exit velocity around a particular player's true-talent aev is 8 mph. at this point in the season, marco masher has a total of 10 batted balls with an average exit velocity of 94 mph. given only this information, the best estimate for his true talent exit velocity is closest to which whole number?