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

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 women are sitting at a table eating lunch'. Replace the letter 'e' with 'k' in the sentence.
Example Output: a group of womkn ark sitting at a tablk kating lunch

Example Input: Sentence: 'a group of mormons standing around a woman'. Replace the letter 'a' with 'n' in the sentence.
Example Output:
n group of mormons stnnding nround n womnn