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

Example Input: Sentence: 'an overhead view of a city cross walk on a rainy day features an array of colorful umbrellas'. Replace the letter 's' with 'd' in the sentence.
Example Output: an overhead view of a city crodd walk on a rainy day featured an array of colorful umbrellad

Example Input: Sentence: 'the people are in the library working and studying'. Replace the letter 'r' with 'g' in the sentence.
Example Output: the people age in the libgagy wogking and studying

Example Input: Sentence: 'black and red bicycles are lined up in front of a train'. Replace the letter 'o' with 'w' in the sentence.
Example Output:
black and red bicycles are lined up in frwnt wf a train