TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a gray elephant is in a grassy field'. Find frequency of the letter 'e'

SOLUTION: 3

PROBLEM: Sentence: 'a group of three dogs laying on a kitchen floor'. Find frequency of the letter 'r'

SOLUTION: 3

PROBLEM: Sentence: 'a kid throws a ball to coaches at baseball practice'. Find frequency of the letter 'l'

SOLUTION:
4