TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a black bear sitting in the grass taking a rest'. Find frequency of the letter 'a'

SOLUTION: 6

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

SOLUTION: 1

PROBLEM: Sentence: 'man seen operating a bus from a mirror'. Find frequency of the letter 'n'

SOLUTION:
3