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

Example Input: Sentence: 'a back pack and lap top sit on the kitchen counter'. Replace the letter 't' with 'k' in the sentence.
Example Output: a back pack and lap kop sik on khe kikchen counker

Example Input: Sentence: 'a open entrance leading to a set of closed doors'. Replace the letter 'd' with 'f' in the sentence.
Example Output: a open entrance leafing to a set of closef foors

Example Input: Sentence: 'a sidewalk with various signage and people walking on the street'. Replace the letter 'l' with 'k' in the sentence.
Example Output:
a sidewakk with various signage and peopke wakking on the street