instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'an commercial airline airplane flies above the clouds'. Find frequency of the letter 'n'
answer:
3


question:
Sentence: 'a picture of a machine built next to a street'. Find frequency of the letter 'x'
answer:
1


question:
Sentence: 'a tasty sandwich with vegetables on a white plate'. Find frequency of the letter 'n'
answer:

2