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

Sentence: 'a sheep in a field in front of other sheep'. Find frequency of the letter 'f'
3

Sentence: 'a knife a cutting board some bananas and a toaster'. Find frequency of the letter 'i'
2

Sentence: 'to see a lot of planes, go to an air museum'. Find frequency of the letter 'o'

5