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

[EX Q]: Sentence: 'a passenger bus that is driving down the street'. Find frequency of the letter 'r'
[EX A]: 3

[EX Q]: Sentence: 'a plane with smoke coming from the tips of both wings'. Find frequency of the letter 'c'
[EX A]: 1

[EX Q]: Sentence: 'a small elephant standing next to a lush green field'. Find frequency of the letter 'x'
[EX A]:
1