TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a young boy bouncing a tennis ball on a tennis racquet'. Find frequency of the letter 'a'

SOLUTION: 5

PROBLEM: Sentence: 'hand holding a white calculator inside a store'. Find frequency of the letter 'o'

SOLUTION: 3

PROBLEM: Sentence: 'a person on a surfboard riding a wave'. Find frequency of the letter 'n'

SOLUTION:
3