instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a red fire hydrant opened and spilling water'. Find frequency of the letter 'd'
answer:
4


question:
Sentence: 'this yellow fire hydrant sits in a grass field'. Find frequency of the letter 'i'
answer:
5


question:
Sentence: 'a surfer rides a wave in the ocean'. Find frequency of the letter 's'
answer:

2