Permutation question about area codes?

For years, telephone area codes in the United States and Canada consisted

of a sequence of three digits. The 炉rst digit was an integer between 2 and 9; the second

digit was either 0 or 1; the third digit was any integer between 1 and 9. How many area

codes were possible ? How many area codes starting with a 4 were possible ?Permutation question about area codes?
qa

ways for 1st digit = 8

ways for 2nd digit = 2

ways for 3rd digit = 9

thus total ways = 8*2*9 144



qb

if 1st digit has to be 4,

total ways = 1*2*9 = 18