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

[Q]: Sentence: 'a notebook and pen are left on a park bench'. Find frequency of the letter 'e'
[A]: 5


[Q]: Sentence: 'vanity sitting atop a base with two doors and a mirror overhead'. Find frequency of the letter 'n'
[A]: 3


[Q]: Sentence: 'a large black dog standing inside of a kitchen'. Find frequency of the letter 'a'
[A]:
5