TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'two pepperoni pizzas and a cup on a counter'. Find frequency of the letter 'u'

SOLUTION: 2

PROBLEM: Sentence: 'an orange cat sitting on the ground next to a  purse'. Find frequency of the letter 's'

SOLUTION: 2

PROBLEM: Sentence: 'the bagel sandwich has many ingredients inside of it'. Find frequency of the letter 's'

SOLUTION:
4