instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a small white plane sitting on top of the ocean'. Find frequency of the letter 'e'
answer:
4


question:
Sentence: 'a person working at an airport, outside of an airplane'. Find frequency of the letter 'r'
answer:
5


question:
Sentence: 'a black horse with a white dot on its forehead'. Find frequency of the letter 't'
answer:

4