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

Sentence: 'a crowd of people standing in front of a green train'. Find frequency of the letter 'g'
2

Sentence: 'two men sitting quietly on a park bench'. Find frequency of the letter 'a'
2

Sentence: 'a bathroom with records mounted to the wall around a white toilet'. Find frequency of the letter 'w'
3