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

[Q]: Sentence: 'the two dogs are playing in the pen together'. Find frequency of the letter 'o'
[A]: 3


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


[Q]: Sentence: 'living room that has boxes packed for moving'. Find frequency of the letter 'p'
[A]:
1