TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'man in red shirt with black suitcase standing outside of building'. Find frequency of the letter 'i'

SOLUTION: 8

PROBLEM: Sentence: 'a microwave oven with a yellow note on the door'. Find frequency of the letter 'w'

SOLUTION: 3

PROBLEM: Sentence: 'rider jumps horse over brick wall during a competition'. Find frequency of the letter 'r'

SOLUTION:
6