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

[Q]: Sentence: 'two laptop computers sitting on top of a white table'. Find frequency of the letter 'f'
[A]: 1


[Q]: Sentence: 'a yellow fire hydrant in the forefront of a roadway'. Find frequency of the letter 'r'
[A]: 5


[Q]: Sentence: 'a bird is picking a berry from a tree'. Find frequency of the letter 'a'
[A]:
3