instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a gray elephant is in a grassy field'. Find frequency of the letter 'e'
answer:
3


question:
Sentence: 'two persons standing outside a moving sub train'. Find frequency of the letter 'a'
answer:
3


question:
Sentence: 'the man in a leather jacket sits near many wine glasses'. Find frequency of the letter 'n'
answer:

5