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

Ex Input:
Sentence: 'a woman sitting on a bench under a gazebo'. Replace the letter 's' with 'u' in the sentence.

Ex Output:
a woman uitting on a bench under a gazebo

Ex Input:
Sentence: 'a man is somewhat hard to be seen in the wave, on his board'. Replace the letter 's' with 'b' in the sentence.

Ex Output:
a man ib bomewhat hard to be been in the wave, on hib board

Ex Input:
Sentence: 'a group of different colored surfboards and different sizes'. Replace the letter 'i' with 'j' in the sentence.

Ex Output:
a group of djfferent colored surfboards and djfferent sjzes