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

Ex Input:
Sentence: 'an older red airplane is going straight up'. Replace the letter 'h' with 'z' in the sentence.

Ex Output:
an older red airplane is going straigzt up

Ex Input:
Sentence: 'a group of three giraffes standing around a fence'. Replace the letter 't' with 'a' in the sentence.

Ex Output:
a group of ahree giraffes saanding around a fence

Ex Input:
Sentence: '4 people seem to be playing the nintendo wii on a large screen'. Replace the letter 'w' with 'g' in the sentence.

Ex Output:
4 people seem to be playing the nintendo gii on a large screen