TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a dog laying on the back of a boat in the water'. Find frequency of the letter 't'

SOLUTION: 4

PROBLEM: Sentence: 'a train station with a train pulling into the platform'. Find frequency of the letter 'i'

SOLUTION: 6

PROBLEM: Sentence: 'a fluffy dog is walking up the beach'. Find frequency of the letter 'i'

SOLUTION:
2