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

Example Input: Sentence: 'a group of sheep is standing in a grassy field'. Replace the letter 'g' with 'p' in the sentence.
Example Output: a proup of sheep is standinp in a prassy field

Example Input: Sentence: 'a man that is on the back of an elephant'. Replace the letter 'c' with 'd' in the sentence.
Example Output: a man that is on the badk of an elephant

Example Input: Sentence: 'three vases with flowers in them on a white background'. Replace the letter 't' with 'h' in the sentence.
Example Output:
hhree vases wihh flowers in hhem on a whihe background