TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a group of men standing on the side of a boat'. Find frequency of the letter 'o'

SOLUTION: 5

PROBLEM: Sentence: 'some giraffes moving across a big grass field'. Find frequency of the letter 'e'

SOLUTION: 3

PROBLEM: Sentence: 'a lamp post clock set in a circular, fenced garden'. Find frequency of the letter 's'

SOLUTION:
2