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

[EX Q]: Sentence: 'a man riding a white surfboard on a large wave'. Find frequency of the letter 'a'
[EX A]: 7

[EX Q]: Sentence: 'a man sitting inside a green military truck talking to someone'. Find frequency of the letter 'i'
[EX A]: 7

[EX Q]: Sentence: 'a tennis player getting ready to hit a serve'. Find frequency of the letter 't'
[EX A]:
5