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

Ex Input:
Sentence: 'a variety of a different type of vegetables'. Find frequency of the letter 't'

Ex Output:
4

Ex Input:
Sentence: 'many different species of sheep in display at a museum'. Find frequency of the letter 'h'

Ex Output:
1

Ex Input:
Sentence: 'child in a body of water wearing a life preserver and water skis'. Find frequency of the letter 'e'

Ex Output:
7