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: 'group of cars on the road with the sun setting behind it'. Find frequency of the letter 'd'

SOLUTION: 2

PROBLEM: Sentence: 'overhead picture of a zoo exhibit with covers for sun'. Find frequency of the letter 'o'

SOLUTION:
6