Detailed Instructions: In this task, you need to replace a letter in the sentence with another given letter.
See one example below:
Problem: Sentence: 'group of motorcycle motorists trying to merge into traffic'. Replace the letter 'o' with 'n' in the sentence.
Solution: grnup nf mntnrcycle mntnrists trying tn merge intn traffic
Explanation: The letter 'o' has been replaced in the letter 'n'.

Problem: Sentence: 'a man outside with an umbrela in the sun'. Replace the letter 'a' with 'x' in the sentence.
Solution:
x mxn outside with xn umbrelx in the sun