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

[Q]: Sentence: 'a man and a woman are walking down the street with an umbrella over their heads'. Find frequency of the letter 'w'
[A]: 4


[Q]: Sentence: 'a tower with some bright lights and clocks on it'. Find frequency of the letter 'h'
[A]: 3


[Q]: Sentence: 'a wooden desk topped with a desktop computer'. Find frequency of the letter 'd'
[A]:
4