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

Example Input: Sentence: 'a yellow fire truck parked in a parking lot'. Replace the letter 'a' with 'y' in the sentence.
Example Output: y yellow fire truck pyrked in y pyrking lot

Example Input: Sentence: 'a table full of various types of cellphones, pdas and pagers'. Replace the letter 's' with 'f' in the sentence.
Example Output: a table full of variouf typef of cellphonef, pdaf and pagerf

Example Input: Sentence: 'two dogs in a back yard with pots with flowers'. Replace the letter 'w' with 'u' in the sentence.
Example Output:
tuo dogs in a back yard uith pots uith flouers