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

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


[Q]: Sentence: 'a train station with a train pulling into the platform'. Find frequency of the letter 'i'
[A]: 6


[Q]: Sentence: 'a person holding skis standing in front of a cabin'. Find frequency of the letter 'd'
[A]:
2