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

Example Input: Sentence: 'a toddler on skis being held up by a grownup'. Replace the letter 'o' with 'k' in the sentence.
Example Output: a tkddler kn skis being held up by a grkwnup

Example Input: Sentence: 'a crowd watches as giraffes graze the tree tops at the zoo'. Replace the letter 't' with 'q' in the sentence.
Example Output: a crowd waqches as giraffes graze qhe qree qops aq qhe zoo

Example Input: Sentence: 'an older woman is dressed in clothes to play tennis'. Replace the letter 'l' with 'a' in the sentence.
Example Output:
an oader woman is dressed in caothes to paay tennis