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 crowd of people standing in front of a green train'. Find frequency of the letter 'g'
[EX A]: 2

[EX Q]: Sentence: 'a group of woman chasing a soccer ball'. Find frequency of the letter 'c'
[EX A]:
3