instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'two metal  benches on an empty train platform'. Find frequency of the letter 'n'
answer:
4


question:
Sentence: 'two boys are doing skateboard jumps in the street'. Find frequency of the letter 's'
answer:
4


question:
Sentence: 'a grilled sandwich on a white plate with some french fries'. Find frequency of the letter 'a'
answer:

4