instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a silver train crossing the road on tracks'. Find frequency of the letter 'r'
answer:
5


question:
Sentence: 'the receipts from a meal at a restaurant are for  a sandwich, chili, and apple'. Find frequency of the letter 'u'
answer:
1


question:
Sentence: 'group of people outside and one pointing up to the sky'. Find frequency of the letter 'k'
answer:

1