How many different 6letter words can be made a if the first

How many different 6-letter words can be made

a. if the first letter must be D or W and no letter may be repeated?

b. if repeats are allowed (but the first letter is D or W)?

c. How many of the 6-letter words (starting with D or W) with no respects end in R?

First letter is fixed D or W

Hence I letter can be selected in 2 ways, second in remainning 25 ways, 3rd 24.....

Hence total no of different 6 letter words if no repitition is allowed

= 2(25)(24)(23)(22)(21)

= 12751200

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b) I letter can be in two ways

II,iii iv can be any one of 26 letters.

Hence total no of letters = 2(26)⁴

= 913952

c) Start letter has 2 choices and end letter only R

The remaining 4 letters can be any one of 24, then 23, then 22 and 21 as no repitition is allowed

Hence total no of words = 2(1) 24(23)(22)(21)

=510048