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 fire hydrant in the forefront of a roadway'. Find frequency of the letter 'r'

SOLUTION: 5

PROBLEM: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'

SOLUTION: 1

PROBLEM: Sentence: 'here is a kitten on the keys, keyboard, that is. this long-haired cat is sitting parallel to the top of the keyboard'. Find frequency of the letter 'e'

SOLUTION:
11