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

[EX Q]: Sentence: 'a person dressed all in black snowboarding down a slope'. Find frequency of the letter 'e'
[EX A]: 4

[EX Q]: Sentence: 'group of snowboarders on a snowy trail overlooking a mountain'. Find frequency of the letter 'r'
[EX A]: 5

[EX Q]: Sentence: 'a microwave is kept with its door open'. Find frequency of the letter 'o'
[EX A]:
4