Suppose that a $$word$$ is any string of seven letters of the alphabet, with repeated letters allowed. How many words begin with AAB in some order? Suppose that a $$word$$ is any string of seven letters of the alphabet, with repeated letters allowed. How many words have exactly one vowel? Suppose that a $$word$$ is any string of seven letters of the alphabet, with repeated letters allowed. How many words begin with A or end with B$?$ Suppose that a $$word$$ is any string of seven letters of the alphabet, with repeated letters allowed. How many words begin with A or B$?$Suppose that a $$word$$ is any string of seven letters of the alphabet, with repeated letters allowed. How many words begin with R and end with T$?$Suppose that a $$word$$ is any string of seven letters of the alphabet, with repeated letters allowed. How many words are there?