Problem Solving (PS) | Re: The difference 942 249 is a positive multiple of 7. If a, b, and c a

­The difference 942 − 249 is a positive multiple of 7. If a, b, and c are nonzero digits, how many 3-digit numbers abc are possible such that the difference abc − cba is a positive multiple of 7 ?

A. 142
B. 71
C. 99
D. 20
E. 18

We should include the cases of b=0 right? abc-cba needs to be a positive multiple of 7. So b can be 0 for eg. 801-108= 693 which is a positive multiple of 7 but this isn't counted in the solution. Shouldn't the answer be 20?