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

[Q]: Sentence: 'a man in a black wet suit rides an orange surfboard on the water'. Find frequency of the letter 'o'
[A]: 3


[Q]: Sentence: 'this is a close up view of a tennis player during the game'. Find frequency of the letter 't'
[A]: 3


[Q]: Sentence: 'a marina filled with lots of boats under a blue sky'. Find frequency of the letter 'r'
[A]:
2