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

[Q]: Sentence: 'three elephants walk up a dirt trail from the water'. Find frequency of the letter 'l'
[A]: 3

[Q]: Sentence: 'a log in the water with three birds perched on it'. Find frequency of the letter 'r'
[A]: 4

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