TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a yellow and green train on a train track in a wooded area'. Find frequency of the letter 'o'

SOLUTION: 4

PROBLEM: Sentence: 'the street sign is next to a curved road'. Find frequency of the letter 's'

SOLUTION: 3

PROBLEM: Sentence: 'a man riding skis behind another person towing a bag'. Find frequency of the letter 'r'

SOLUTION:
3