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

[Q]: Sentence: 'pizza with different vegetables sitting on top of a wooden slab'. Find frequency of the letter 'o'
[A]: 5


[Q]: Sentence: 'a train is sitting at a train station'. Find frequency of the letter 'r'
[A]: 2


[Q]: Sentence: 'a sheep in a field in front of other sheep'. Find frequency of the letter 'f'
[A]:
3