TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a silver train crossing the road on tracks'. Find frequency of the letter 'r'

SOLUTION: 5

PROBLEM: Sentence: 'a man in his car eating a donut'. Find frequency of the letter 'm'

SOLUTION: 1

PROBLEM: Sentence: 'a person that is playing in a tennis game'. Find frequency of the letter 'i'

SOLUTION:
4