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

[EX Q]: Sentence: 'several zebras  and a giraffe in an enclosure'. Find frequency of the letter 's'
[EX A]: 3

[EX Q]: Sentence: 'a person on a skateboard going down a ramp'. Find frequency of the letter 'n'
[EX A]: 4

[EX Q]: Sentence: 'a man using his cell phone by a sign that says no cellphones'. Find frequency of the letter 'i'
[EX A]:
3