TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a herd of zebra standing on top of a grass covered field'. Find frequency of the letter 'e'

SOLUTION: 5

PROBLEM: Sentence: 'a baseball player dropping his bat and starting to run'. Find frequency of the letter 'o'

SOLUTION: 2

PROBLEM: Sentence: 'nice flowers on a white vase and some models besides'. Find frequency of the letter 'd'

SOLUTION:
3