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

Example Input: Sentence: 'closeup of two teddy bears in red scarves and a brown teddy bear'. Replace the letter 'i' with 'y' in the sentence.
Example Output: closeup of two teddy bears yn red scarves and a brown teddy bear

Example Input: Sentence: 'a motorcycle sitting on the side of the road by grass'. Replace the letter 'r' with 't' in the sentence.
Example Output: a mototcycle sitting on the side of the toad by gtass

Example Input: Sentence: 'a man adjusts a mirror on his motorcycle'. Replace the letter 'l' with 'g' in the sentence.
Example Output:
a man adjusts a mirror on his motorcycge