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

[Q]: Sentence: 'a table topped with a cupcake on a picture of a cupcake'. Find frequency of the letter 'o'
[A]: 3


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


[Q]: Sentence: 'a stop sign and no stopping or standing sign on a street at night'. Find frequency of the letter 'a'
[A]:
5