TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a man riding on the back of a white horse next to other horses'. Find frequency of the letter 'o'

SOLUTION: 6

PROBLEM: Sentence: 'a small boat travels on the water next to the shore'. Find frequency of the letter 'a'

SOLUTION: 5

PROBLEM: Sentence: 'a train going over a bridge with some buildings in the background'. Find frequency of the letter 'd'

SOLUTION:
3