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

Sentence: 'a plastic container next to a toilet on a wooden box'. Find frequency of the letter 'i'
3

Sentence: 'a large cooked pizza on a dining table'. Find frequency of the letter 'n'
3

Sentence: 'a woman in black jacket eating a hotdog'. Find frequency of the letter 'n'

3