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

Ex Input:
Sentence: 'oranges are sitting in a bowl on a table'. Find frequency of the letter 'a'

Ex Output:
5

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: 'a gray and white farm animal is laying in the grass'. Find frequency of the letter 'l'

Ex Output:
2