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

[EX Q]: Sentence: 'a man using a video game controller in a room'. Find frequency of the letter 'n'
[EX A]: 4

[EX Q]: Sentence: 'a stop sign near a rail road crossing sign'. Find frequency of the letter 'g'
[EX A]: 3

[EX Q]: Sentence: 'a boy in white shirt doing a trick on a skateboard'. Find frequency of the letter 'k'
[EX A]:
2