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 dog has found a rather large stick for playing fetch'. Find frequency of the letter 't'
[EX A]: 3

[EX Q]: Sentence: 'a person is looking out the window in a hotel room'. Find frequency of the letter 'e'
[EX A]:
3