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

[EX Q]: Sentence: 'a chair and umbrella on a sandy beach'. Find frequency of the letter 's'
[EX A]: 1

[EX Q]: Sentence: 'a group of people stand inside of a big room'. Find frequency of the letter 'o'
[EX A]: 6

[EX Q]: Sentence: 'two trains taking off from a station with cameras'. Find frequency of the letter 'k'
[EX A]:
1