Answer:
The option "C (7,999,999)" is correct.
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Explanation:
To find the total possible phone numbers just multiply the total number of possible options in each category
i.e. there are total 7 categories
--> one category = A
--> one category = B
--> one category = C
--> four categories = X
NOW the possible options in category A are from 2-9 (as given)
THUS count the numbers from 2 to 9 which are 2, 3, 4, 5, 6, 7, 8 & 9 and are 8 options
Similarly in category B (0-9) are 10 options
and in this way in all the remaining categories (C and Xs) are also 10, 10 options
SO
you have to write 8 in place of A and 10 in place of all other categories
i.e. 8,10,10, 10,10,10,10
THEN multiply all these
I.e. 8×10×10 ×10×10×10×10
= 8,000,000
NOW there is also an exception of one number that is given as 867-5309
So SUBTRACT one from the above figure i.e.
total possible phone numbers = 8,000,000 - 1 = 7,999,999
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