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

[Q]: Sentence: 'a young boy wearing black and holding a skateboard on the sidewalk'. Find frequency of the letter 'n'
[A]: 5

[Q]: Sentence: 'one woman is arranging the other woman's hair'. Find frequency of the letter 'o'
[A]: 4

[Q]: Sentence: 'bear like caricature on wire with tall building with clocks and spire in background'. Find frequency of the letter 'r'
[A]:
6