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

[Q]: Sentence: 'a downhill skier with snow plumes behind them'. Find frequency of the letter 'i'
[A]: 4


[Q]: Sentence: 'a big bear walks through some grass'. Find frequency of the letter 'a'
[A]: 4


[Q]: Sentence: 'a family on a houseboat takes shelter under umbrella as they cruise down a canal'. Find frequency of the letter 'n'
[A]:
4