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

[Q]: Sentence: 'a glass bowl of raw broccoli, a ceramic bowl of raw green chili peppers, and steel bowl of raw daikon'. Find frequency of the letter 'a'
[A]: 9


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


[Q]: Sentence: 'a person with a frisbee in a yard'. Find frequency of the letter 'i'
[A]:
3