Converting a Null$-$Terminated String to Lowercase in MIPS Assembly

For the homework, you will be using the load byte$($lb$)$ and store byte$($sb$)$ instructions. It works similiarly to the load word instruction but instead loading and storing all $32$ bit to and from registers$/$memory it only stores and loads the first $8$ bits. Other than that it works the exact same way as load$/$store word.

You are given a null terminated string, denoted by ascii value $0.$ The base address of this string variable is stored in register $s$0.$

Convert valid character in the string, A$-$Z to lowercase letters. Punctuations, lowercase letters, numbers, spaces and other non alphanumeric should not be affected.

For those who need a refresher, string are simply an array of chars, and chars are $1$ byte.