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

[EX Q]: Sentence: 'a railroad train pulling up to the train platform'. Find frequency of the letter 'o'
[EX A]: 3

[EX Q]: Sentence: 'there is a zebra that is walking enar a car'. Find frequency of the letter 'r'
[EX A]: 4

[EX Q]: Sentence: 'a giraffe standing next to a pile or rocks'. Find frequency of the letter 'a'
[EX A]:
4