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

[EX Q]: Sentence: 'a couple of girls are hanging out at a restaurant'. Find frequency of the letter 'l'
[EX A]: 2

[EX Q]: Sentence: 'a person is riding in a cart pulled by a horse'. Find frequency of the letter 'a'
[EX A]: 4

[EX Q]: Sentence: 'a crane stands on the edge of a rocky shore'. Find frequency of the letter 's'
[EX A]:
3