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

Example Input: Sentence: 'a busy intersection with cars moving at night'. Replace the letter 's' with 'f' in the sentence.
Example Output: a bufy interfection with carf moving at night

Example Input: Sentence: 'three colorful knit bear toys with button eyes'. Replace the letter 'r' with 'z' in the sentence.
Example Output: thzee colozful knit beaz toys with button eyes

Example Input: Sentence: 'the young boy is skateboarding on the sidewalk'. Replace the letter 'e' with 'c' in the sentence.
Example Output:
thc young boy is skatcboarding on thc sidcwalk