In this task, you need to count the number of times the given letter appears in the given sentence.
--------
Question: Sentence: 'a plastic container next to a toilet on a wooden box'. Find frequency of the letter 'i'

Answer: 3

Question: Sentence: 'a train is sitting at a train station'. Find frequency of the letter 'r'

Answer: 2

Question: Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'

Answer:
7