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

[Q]: Sentence: 'a girl that has a kite in the air'. Find frequency of the letter 'r'
[A]: 2

[Q]: Sentence: 'a bird in a tree looking up at branches'. Find frequency of the letter 'e'
[A]: 3

[Q]: Sentence: 'three cows are lying down near a road'. Find frequency of the letter 'l'
[A]:
1