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

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

Sentence: 'the man is holding a plastic sled with snow in it next to a child'. Find frequency of the letter 'g'
1

Sentence: 'a bear in a field of green grass with trees in the background'. Find frequency of the letter 's'

3