How many different 5-letter words can be made:
a. if the first letter must be B, Y, Q, or N and no letter may be repeated?
b. if repeats are allowed (but the first letter is B, Y, Q, or N)?
c. How mSolve the given Problem (Students)
• Define RE, where n a (W) mod 3 = 0
• Define RE, where 2nd last letter should be “b”
• Define RE, whenever “a” appears, it should be followed by 2b’s
• Define RE,
• IF start with “a” THEN must contain “bb” anywhere
• IF start with “b” THEN must contain “aa” anywhere