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

[EX Q]: Sentence: 'a woman at a table checking her cell phone'. Find frequency of the letter 'a'
[EX A]: 5

[EX Q]: Sentence: 'a dog has found a rather large stick for playing fetch'. Find frequency of the letter 't'
[EX A]: 3

[EX Q]: Sentence: 'a person holding an open umbrella near a tree'. Find frequency of the letter 'a'
[EX A]:
5