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

Example Input: Sentence: 'a tennis player throwing a ball at the ground'. Replace the letter 'r' with 'f' in the sentence.
Example Output: a tennis playef thfowing a ball at the gfound

Example Input: Sentence: 'a woman is standing on a street curb'. Replace the letter 'a' with 't' in the sentence.
Example Output: t womtn is sttnding on t street curb

Example Input: Sentence: 'a group of people on skis. standing on the snow covered ground together'. Replace the letter 'n' with 'w' in the sentence.
Example Output:
a group of people ow skis. stawdiwg ow the swow covered grouwd together