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

Sentence: 'three men in military suits are sitting on a bench,'. Find frequency of the letter 'a'
3

Sentence: 'a person riding a camel in front of a truck'. Find frequency of the letter 't'
2

Sentence: 'a view of snowy mountains and three people standing in the snow near a slope'. Find frequency of the letter 'e'
8