instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a white police vehicle parked on a paved street'. Find frequency of the letter 'a'
answer:
4


question:
Sentence: 'two persons standing outside a moving sub train'. Find frequency of the letter 'a'
answer:
3


question:
Sentence: 'a group of young men playing games on the nintendo wii'. Find frequency of the letter 'y'
answer:

2