The answer is 24 bits
ASCII has encoding for numbers and every character of the alphabet. For instance, if you take 150 as an integer, you will need to store it as 8 bits. If it is taken as 3 characters, then it will require 24 total bits (8 * 3), that is 8 bits per character. It is good to note that the 8-bit byte is the most common storage element and enjoys 256 characters from the original 7-bit which has become a bit synonymous.