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

Ex Input:
Sentence: 'a white bathroom sink sitting next to a toilet'. Find frequency of the letter 'i'

Ex Output:
5

Ex Input:
Sentence: 'people plating cake in an office meeting room'. Find frequency of the letter 'g'

Ex Output:
2

Ex Input:
Sentence: 'a man who is dribbling a soccer ball'. Find frequency of the letter 'c'

Ex Output:
2