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

Example Input: Sentence: 'a small dog in the back compartment of a backpack'. Replace the letter 'c' with 'd' in the sentence.
Example Output: a small dog in the badk dompartment of a badkpadk

Example Input: Sentence: 'a tennis racket is sitting in the middle of a tennis field'. Replace the letter 'i' with 'f' in the sentence.
Example Output: a tennfs racket fs sfttfng fn the mfddle of a tennfs ffeld

Example Input: Sentence: 'three metal spoons reflect an image of the outdoors'. Replace the letter 'o' with 'f' in the sentence.
Example Output:
three metal spffns reflect an image ff the futdffrs