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

[EX Q]: Sentence: 'small airplane in the process of taking off'. Find frequency of the letter 'e'
[EX A]: 3

[EX Q]: Sentence: 'a white and blue plate topped with meat and a salad'. Find frequency of the letter 'u'
[EX A]: 1

[EX Q]: Sentence: 'a bus in the street with a bike on the front of it'. Find frequency of the letter 'n'
[EX A]:
3