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

[Q]: Sentence: 'a group of people standing on grass with a train in the background'. Find frequency of the letter 'n'
[A]: 6


[Q]: Sentence: 'two computers and a laptop set up on a desk'. Find frequency of the letter 'r'
[A]: 1


[Q]: Sentence: 'someone in a red hat standing on a snowy hill'. Find frequency of the letter 'o'
[A]:
4