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

Sentence: 'the little girl is flying her kite in the field'. Find frequency of the letter 'i'
7

Sentence: 'a plastic plastic plate topped with three different type of food'. Find frequency of the letter 'l'
3

Sentence: 'a couple of white street signs sitting on top of a pole'. Find frequency of the letter 'u'

1