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

[EX Q]: Sentence: 'people playing wii bowling in a modern library'. Find frequency of the letter 'o'
[EX A]: 3

[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 man sitting on a motorcycle near two other men'. Find frequency of the letter 'r'
[EX A]:
3