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

Sentence: 'a white bathroom sink sitting next to a toilet'. Find frequency of the letter 'i'
5

Sentence: 'a couple of buses parked on the side of the street'. Find frequency of the letter 'b'
1

Sentence: 'a girl in a school uniform smiles at the camera'. Find frequency of the letter 'l'

3