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

Example Input: Sentence: 'a giraffe sticks its tongue out in the air'. Replace the letter 'e' with 'l' in the sentence.
Example Output: a giraffl sticks its tongul out in thl air

Example Input: Sentence: 'a man walking a horse on a dirt track'. Replace the letter 't' with 's' in the sentence.
Example Output: a man walking a horse on a dirs srack

Example Input: Sentence: 'a girl flies a kite in front of a large building'. Replace the letter 'a' with 'j' in the sentence.
Example Output:
j girl flies j kite in front of j ljrge building