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: 'a group of people are playing soccer on a beach'. Find frequency of the letter 'l'
[EX A]: 2

[EX Q]: Sentence: 'a large white fridge open and sitting outside'. Find frequency of the letter 'f'
[EX A]:
1