In this task, you need to replace a letter in the sentence with another given letter.

Example Input: Sentence: 'three young school girls waiting on a subway train platform'. Replace the letter 't' with 'o' in the sentence.
Example Output: ohree young school girls waioing on a subway orain plaoform

Example Input: Sentence: 'a photo of a woman milking a brown cow'. Replace the letter 'k' with 'q' in the sentence.
Example Output: a photo of a woman milqing a brown cow

Example Input: Sentence: 'three people on a lake try their hand at watersports'. Replace the letter 't' with 'p' in the sentence.
Example Output:
phree people on a lake pry pheir hand ap wapersporps