instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a picture of a machine built next to a street'. Find frequency of the letter 'x'
answer:
1


question:
Sentence: 'a herd of zebra standing on top  of a grass covered field'. Find frequency of the letter 'e'
answer:
5


question:
Sentence: 'a refrigerator filled with bottles of milk and food'. Find frequency of the letter 't'
answer:

4