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

[EX Q]: Sentence: 'a stop sign near a rail road crossing sign'. Find frequency of the letter 'g'
[EX A]: 3

[EX Q]: Sentence: 'a person is riding in a cart pulled by a horse'. Find frequency of the letter 'a'
[EX A]: 4

[EX Q]: Sentence: 'a tagged cow with a bell around its neck'. Find frequency of the letter 'o'
[EX A]:
2