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

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


[Q]: Sentence: 'bathroom scene with a black cat going behind the door'. Find frequency of the letter 'e'
[A]: 4


[Q]: Sentence: 'a man who is holding a baseball bat playing baseball'. Find frequency of the letter 'i'
[A]:
3