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

Sentence: 'a police officer who is riding on a horse'. Find frequency of the letter 'p'
1

Sentence: 'a blue train on a track next to another track'. Find frequency of the letter 'c'
2

Sentence: 'a white plastic sewing kit filled with scissors and other things'. Find frequency of the letter 'h'

4