Given an integer x, let f(x) be the sum of the digits of x. Compute the number of positive
integers less than 1000 where f(x) = 2.  Choose the correct choice from the following options:  A) 2  B) 4  C) 6  D) 8  E) 10
We do casework on the number of digits:   (a) The number has 1 digit. The only valid number is 2.   (b) The number has 2 digits. The only valid numbers are 11 and 20.   (c) The number has 3 digits. The only valid numbers are 101, 110, and 200.   This gives us 6 numbers.   correct answer 6
<result>C</result>
Given an integer x, let f(x) be the sum of the digits of x. Compute the number of positive
integers less than 1000 where f(x) = 2.