Detailed Instructions: In this task, you need to count the number of times the given letter appears in the given sentence.
See one example below:
Problem: Sentence: 'a large group of bananas proped up on several bicycles'. Find frequency of the letter 'e'
Solution: 5
Explanation: The letter 'e' appears 5 times in the sentence.

Problem: Sentence: 'a man standing on one foot holding a skateboard behind him'. Find frequency of the letter 'a'
Solution:
6