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

[EX Q]: Sentence: 'a cat that is standing next to an open suitcase'. Find frequency of the letter 'e'
[EX A]: 3

[EX Q]: Sentence: 'a  woman standing next to a man on a motorcycle in front of a market'. Find frequency of the letter 'l'
[EX A]: 1

[EX Q]: Sentence: 'two people crossing the street in front of a double decker bus in an urban area'. Find frequency of the letter 'n'
[EX A]:
6