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

Sentence: 'a log in the water with three birds perched on it'. Find frequency of the letter 'r'
4

Sentence: 'a large bathroom with marble floor, counter, and bath'. Find frequency of the letter 'f'
1

Sentence: 'a train passing by a field with a grounded airplane'. Find frequency of the letter 'h'

1