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: 'man in air skateboarding on street with building'. Find frequency of the letter 't'
answer:
4

question:
Sentence: 'a blue rail car, followed by a green rail car, driving in a residential neighborhood'. Find frequency of the letter 'e'
answer:
7