instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'small airplane in the process of taking off'. Find frequency of the letter 'e'
answer:
3


question:
Sentence: 'a train on a train track going through a bunch of trees'. Find frequency of the letter 'u'
answer:
2


question:
Sentence: 'a pizza sitting inside of a box on top of a table'. Find frequency of the letter 'i'
answer:

5