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

[EX Q]: Sentence: 'a man is water skiing on a river'. Find frequency of the letter 'r'
[EX A]: 3

[EX Q]: Sentence: 'a bowl of granola, dried fruit, and bananas'. Find frequency of the letter 'u'
[EX A]: 1

[EX Q]: Sentence: 'a close up of a zebra with plant life all around'. Find frequency of the letter 'o'
[EX A]:
3