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

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

[EX Q]: Sentence: 'a bunch of broken down trains sit in a yard'. Find frequency of the letter 'n'
[EX A]: 5

[EX Q]: Sentence: 'a group of guys on a couch watching tv'. Find frequency of the letter 'f'
[EX A]:
1