TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'there is a sandwich with a lot of meat cut in half'. Find frequency of the letter 'a'

SOLUTION: 5

PROBLEM: Sentence: 'a man and several white red and blue airplanes'. Find frequency of the letter 'u'

SOLUTION: 1

PROBLEM: Sentence: 'an orange fire hydrant sitting at the side of the street'. Find frequency of the letter 'i'

SOLUTION:
4