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

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

[EX Q]: Sentence: 'a number of small boats on a beach near an umbrella'. Find frequency of the letter 's'
[EX A]: 2

[EX Q]: Sentence: 'four asian guys sitting down and playing a nintendo wii together'. Find frequency of the letter 'r'
[EX A]:
2