In this task, you need to count the number of times the given letter appears in the given sentence.

[EX Q]: Sentence: 'the small black and white dog holds onto a frisbee'. Find frequency of the letter 'h'
[EX A]: 3

[EX Q]: Sentence: 'the receipts from a meal at a restaurant are for  a sandwich, chili, and apple'. Find frequency of the letter 'u'
[EX A]: 1

[EX Q]: Sentence: 'a girl holding a pet bird in front of a mirror'. Find frequency of the letter 'i'
[EX A]:
5