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: 'oranges are sitting in a bowl on a table'. Find frequency of the letter 'a'
answer:
5


question:
Sentence: 'man in a sleeping bag on the floor using a laptop computer'. Find frequency of the letter 'i'
answer:

3