TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a toasted sub sandwich is next to a salad'. Find frequency of the letter 'a'

SOLUTION: 6

PROBLEM: Sentence: 'a bus is stopped in front of a graphic statue'. Find frequency of the letter 'e'

SOLUTION: 2

PROBLEM: Sentence: 'a girl standing next to a door holding a toothbrush'. Find frequency of the letter 'r'

SOLUTION:
3