Odd letters (1.3.1, 2)

Knuth asks:

Which of the letters {A,B,C,D,E,F,a,b,c,d,e,f} are odd when considered as
(a) hexadecimal digits? (b) ASCII characters?

(a) Since #A = (10)₁₀ we have immediately {B, D, F,b,d,f} are odd when considered as hexadecimal digits.

(b) The ascii for A is #41 and a is #61. Hence we can easily see that {A,C,E,a,c,e} are odd when considered as ASCII characters.