TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a girl sits on a surfboard and smiles'. Find frequency of the letter 'i'

SOLUTION: 3

PROBLEM: Sentence: 'two metal  benches on an empty train platform'. Find frequency of the letter 'n'

SOLUTION: 4

PROBLEM: Sentence: 'a blue bus and a red bus in a parking lot'. Find frequency of the letter 't'

SOLUTION:
1