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

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

Sentence: 'a person on a sidewalk jumping with an umbrella'. Find frequency of the letter 'a'
5

Sentence: 'a small bike propped up next to a larger motor bike'. Find frequency of the letter 'p'

4