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

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

[EX Q]: Sentence: 'a man walking a large elephant down a dirt road'. Find frequency of the letter 'g'
[EX A]: 2

[EX Q]: Sentence: 'large advertising display overlooking traffic on urban roadway'. Find frequency of the letter 'n'
[EX A]:
4