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

[Q]: Sentence: 'a softball player holding the bat on first base'. Find frequency of the letter 't'
[A]: 4


[Q]: Sentence: 'there is a baseball game on and a few people are watching'. Find frequency of the letter 'i'
[A]: 2


[Q]: Sentence: 'a book is setting on a green bench'. Find frequency of the letter 'k'
[A]:
1