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

[Q]: Sentence: 'a young man riding a skateboard near a forest'. Find frequency of the letter 'd'
[A]: 2

[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 black and white toilet sitting in a bathroom next to a plant filled with waste'. Find frequency of the letter 'a'
[A]:
8