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

[EX Q]: Sentence: 'two people under an umbrella while walking down a sidewalk'. Find frequency of the letter 'i'
[EX A]: 3

[EX Q]: Sentence: 'a woman cross country skiing in a competition'. Find frequency of the letter 's'
[EX A]: 3

[EX Q]: Sentence: 'a view of a hotdog sitting on a persons lap'. Find frequency of the letter 'o'
[EX A]:
5