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

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


[Q]: Sentence: 'flower in a vase full of water sitting on a stand '. Find frequency of the letter 'l'
[A]: 3


[Q]: Sentence: 'some people are sitting on the beach underneath and umbrella'. Find frequency of the letter 'n'
[A]:
5