Write a function called smallestLetter that takes in a string argument and returns a char. The char that is returned by this function is the character in the string with the lowest ASCII integer code...

Write a function called smallestLetter that takes in a string argument and returns a char. The char that is returned by this function is the character in the string with the
lowest ASCII integer code.

For example:   smallestLetter("Hello")  returns ‘H’ which is code 72, and smallestLetter("Hello World") returns  ' ' (The space character) which is code 32

Please help me with this problem using c++.