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

[EX Q]: Sentence: 'a child sitting a table with a pizza in front of him'. Find frequency of the letter 'h'
[EX A]: 3

[EX Q]: Sentence: 'a black computer with a screen reading "press any key to begin."'. Find frequency of the letter 'a'
[EX A]: 5

[EX Q]: Sentence: 'two people at a pier holding old toilets'. Find frequency of the letter 'p'
[EX A]:
3