instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
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 tv in a glass mirror in the bathroom'. Find frequency of the letter 'h'
answer:
2


question:
Sentence: 'a cat is sitting near a laptop in a room'. Find frequency of the letter 's'
answer:

2