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

[Q]: Sentence: 'a gray elephant is in a grassy field'. Find frequency of the letter 'e'
[A]: 3


[Q]: Sentence: 'a photo of a couple of people at a convention'. Find frequency of the letter 'v'
[A]: 1


[Q]: Sentence: 'vehicles parked under a tree in a small yard'. Find frequency of the letter 'k'
[A]:
1