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

[EX Q]: Sentence: 'a man and several white red and blue airplanes'. Find frequency of the letter 'u'
[EX A]: 1

[EX Q]: Sentence: 'older man getting ready to swing his bat at a ball on a stand in front of a group of viewers'. Find frequency of the letter 'n'
[EX A]: 7

[EX Q]: Sentence: 'a lot of animals are eating grass on the field'. Find frequency of the letter 'i'
[EX A]:
3