In this task, you need to count the number of times the given letter appears in the given sentence.

[EX Q]: Sentence: 'two pepperoni pizzas and a cup on a counter'. Find frequency of the letter 'u'
[EX A]: 2

[EX Q]: Sentence: 'a man riding on the back of a white horse next to other horses'. Find frequency of the letter 'o'
[EX A]: 6

[EX Q]: Sentence: 'a stop sign that has a light shining on it'. Find frequency of the letter 'n'
[EX A]:
4