When Ximena commutes to work, the amount of time it takes her to arrive is normally distributed with a mean of 38 minutes and a standard deviation of 4.5
minutes. Using the empirical rule, determine the interval that represents the middle
68% of her commute times.

there is no grid

step-by-step explanation:

there is only one way to arrange all the eight relative to each other because they are not distinct. we have

now there are nine places to place an (and not more than one in one place).   because we have four symbols, we need to choose four of these nine places to insert an . order does not matter because the are not distinct.

thus there are 1 · c(9,4) ways, or, if we calculate it,

thus there are 126 ways to form such "words."