instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a railroad train pulling up to the train platform'. Find frequency of the letter 'o'
answer:
3


question:
Sentence: 'a guy riding a bike close to a car in the street'. Find frequency of the letter 'i'
answer:
4


question:
Sentence: 'there are three zebras are walking in a field'. Find frequency of the letter 'e'
answer:

8