instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'several zebras  and a giraffe in an enclosure'. Find frequency of the letter 's'
answer:
3


question:
Sentence: 'a dog laying on the back of a boat in the water'. Find frequency of the letter 't'
answer:
4


question:
Sentence: 'two birds standing on a bench near the water'. Find frequency of the letter 'n'
answer:

5