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

[Q]: Sentence: 'a white bowl filled with peeled orange slices'. Find frequency of the letter 's'
[A]: 2


[Q]: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'
[A]: 1


[Q]: Sentence: 'a passenger train traveling through the country side'. Find frequency of the letter 'a'
[A]:
4