instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a close up of a bird on the outside window sill'. Find frequency of the letter 'c'
answer:
1


question:
Sentence: 'a jet that is flying in the sky with a banner behind it'. Find frequency of the letter 'r'
answer:
1


question:
Sentence: 'many public transit buses in a city street'. Find frequency of the letter 'a'
answer:

3