instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a notebook and pen are left on a park bench'. Find frequency of the letter 'e'
answer:
5


question:
Sentence: 'a small doughnut held in a persons hand'. Find frequency of the letter 'n'
answer:
4


question:
Sentence: 'two men work on a red and black train'. Find frequency of the letter 'n'
answer:

4