Answer :

1 bit must be flipped because:

A=01000001
a=01100001

So to go from a to A you have to change the 3rd bit from 1 to a 0.
AL2006
Only one ... the third bit of the byte, numerical 32.  Every lower-case letter 
has a '1' in that place.  If that bit is changed to '0', then the code represents
the upper-case form of the same letter.