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

[EX Q]: Sentence: 'a street scene looking at the back of the stop sign'. Find frequency of the letter 't'
[EX A]: 6

[EX 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'
[EX A]: 9

[EX Q]: Sentence: 'a group of four baseball players sitting in a dugout'. Find frequency of the letter 'n'
[EX A]:
2