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

Example Input: Sentence: 'a tennis player throwing a ball at the ground'. Replace the letter 'r' with 'f' in the sentence.
Example Output: a tennis playef thfowing a ball at the gfound

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 girrafe walking down a road next to the grass'. Replace the letter 'n' with 'r' in the sentence.
Example Output:
a girrafe walkirg dowr a road rext to the grass