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

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: 'a male holding a baseball bat standing on a big white star'. Replace the letter 'a' with 'i' in the sentence.
Example Output: i mile holding i bisebill bit stinding on i big white stir

Example Input: Sentence: 'a young man riding a skateboard up the side of a ramp'. Replace the letter 'a' with 'c' in the sentence.
Example Output:
c young mcn riding c skctebocrd up the side of c rcmp