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

Ex Input:
Sentence: 'a blue bowl holding mashed bananas and oatmeal with a bottle of sugar and cinnamon sitting beside it'. Find frequency of the letter 'g'

Ex Output:
3

Ex Input:
Sentence: 'a jet flying through the clear blue sky'. Find frequency of the letter 'g'

Ex Output:
2

Ex Input:
Sentence: 'a pizza pan with a pizza covered in vegetables and cheese'. Find frequency of the letter 'i'

Ex Output:
4