Find the total number of different arrangements of the 8 letters in the word TOMORROW.
Find the total number of different arrangements of the 8 letters in the word TOMORROW that have an R at the beginning and an R at the end, and in which the three Os are not all together.
Four letters are selected at random from the 8 letters of the word TOMORROW.
Find the probability that the selection contains at least one O and at least one R .