instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a group of people standing on grass with a train in the background'. Find frequency of the letter 'n'
answer:
6


question:
Sentence: 'an old woman is holding her cat in front of a camera'. Find frequency of the letter 'r'
answer:
3


question:
Sentence: 'a traffic sign at a street intersection with skyscrapers in the background'. Find frequency of the letter 'f'
answer:

2