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 woman at a table checking her cell phone'. Find frequency of the letter 'a'

SOLUTION: 5

PROBLEM: Sentence: 'a large bear laying up against a stone wall'. Find frequency of the letter 'n'

SOLUTION:
3