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

[EX Q]: Sentence: 'the interior of a living and dining room'. Find frequency of the letter 'i'
[EX A]: 6

[EX Q]: Sentence: 'a small boy in a high chair eating a cupcake'. Find frequency of the letter 'i'
[EX A]: 4

[EX Q]: Sentence: 'a person in red chopping green apples under an umbrella'. Find frequency of the letter 'n'
[EX A]:
6