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

Sentence: 'a man serving himself pizza in a wooden booth'. Find frequency of the letter 'n'
4

Sentence: 'two pepperoni pizzas and a cup on a counter'. Find frequency of the letter 'u'
2

Sentence: 'man in black suit and woman in black outfit with leather purse'. Find frequency of the letter 'a'

6