In this task, you need to count the number of times the given letter appears in the given sentence.

[Q]: Sentence: 'a bathroom with a sink, counter top, and mirror is shown'. Find frequency of the letter 'i'
[A]: 4


[Q]: Sentence: 'a woman at a table checking her cell phone'. Find frequency of the letter 'a'
[A]: 5


[Q]: Sentence: 'a batter and catcher during a baseball game'. Find frequency of the letter 'n'
[A]:
2