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 people having dinner and drinking wine'. Find frequency of the letter 'r'

SOLUTION: 3

PROBLEM: Sentence: 'a woman is playing an interactive video game'. Find frequency of the letter 't'

SOLUTION: 2

PROBLEM: Sentence: 'a doggie bed on the floor in the doorway'. Find frequency of the letter 'd'

SOLUTION:
3