TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a sailboat is floating near the rocky shore of a beach'. Find frequency of the letter 'o'

SOLUTION: 5

PROBLEM: Sentence: 'a train on a train track going through a bunch of trees'. Find frequency of the letter 'u'

SOLUTION: 2

PROBLEM: Sentence: 'a picture of a man with a mustache holding a racket'. Find frequency of the letter 'a'

SOLUTION:
7