instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a person on a sidewalk jumping with an umbrella'. Find frequency of the letter 'a'
answer:
5


question:
Sentence: 'pedestrian in stripe clothing standing on street corner'. Find frequency of the letter 's'
answer:
4


question:
Sentence: 'there is a man riding a wave on a surfboard'. Find frequency of the letter 'r'
answer:

4