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

[Q]: Sentence: 'some sheep are standing in a grassy field'. Find frequency of the letter 'n'
[A]: 3


[Q]: Sentence: 'a bus is driving on the street behind some cars'. Find frequency of the letter 'a'
[A]: 2


[Q]: Sentence: 'a student at a school enjoys a large bowl of noodles for lunch'. Find frequency of the letter 'o'
[A]:
8