TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a notebook and pen are left on a park bench'. Find frequency of the letter 'e'

SOLUTION: 5

PROBLEM: Sentence: 'a glass vase sits between two statues'. Find frequency of the letter 'o'

SOLUTION: 1

PROBLEM: Sentence: 'a large cat is sitting in front of a window'. Find frequency of the letter 'r'

SOLUTION:
2