How many bits must be flipped (i. e. changed from 0 to 1 or from 1 to 0) in order to capitalize a lowercase 'a' that’s represented in ascii?

Lowercase a is decimal 97 ; upper case is decimal 65

It's easier to think of them in octal, however: a = octal 141, and A is octal 101

octal to binary is easy, each digit is three bits. 
141 = 001 100 001 
101 = 001 000 001

So, how many bits are changed above?