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

[Q]: Sentence: 'slices of orange are arranged on a plate'. Find frequency of the letter 's'
[A]: 2


[Q]: Sentence: 'a train is sitting at a train station'. Find frequency of the letter 'r'
[A]: 2


[Q]: Sentence: 'a person on a tennis court swinging to hit a tennis ball, with a crowd looking'. Find frequency of the letter 'i'
[A]:
7