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

Example Input: Sentence: 'a number of people sitting on chairs near each other'. Replace the letter 'c' with 'm' in the sentence.
Example Output: a number of people sitting on mhairs near eamh other

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: 'two cyclists wearing helmets and cycling uniforms riding down a paved street'. Replace the letter 'l' with 'k' in the sentence.
Example Output:
two cyckists wearing hekmets and cycking uniforms riding down a paved street