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

[Q]: Sentence: 'a large group of motorcycles parked along a street'. Find frequency of the letter 'a'
[A]: 5


[Q]: Sentence: 'a red building with a crowd of people outside it near the water'. Find frequency of the letter 'e'
[A]: 7


[Q]: Sentence: 'two giraffes mating in the middle of a park reserve'. Find frequency of the letter 'm'
[A]:
2