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

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

[EX Q]: Sentence: 'a black cat laying down on a bed'. Find frequency of the letter 'y'
[EX A]: 1

[EX Q]: Sentence: 'black motorcycle standing on display outside in the sun'. Find frequency of the letter 'n'
[EX A]:
5