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: 'oranges are sitting in a bowl on a table'. Find frequency of the letter 'a'

SOLUTION: 5

PROBLEM: Sentence: 'a jet that is flying in the sky'. Find frequency of the letter 't'

SOLUTION:
4