instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a couple of boys in a field playing baseball'. Find frequency of the letter 'i'
answer:
3


question:
Sentence: 'group of snowboarders on a snowy trail overlooking a mountain'. Find frequency of the letter 'r'
answer:
5


question:
Sentence: 'a cow is laying down in the sand'. Find frequency of the letter 'n'
answer:

4