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

Sentence: 'a snow filled mountain with a guy with ski's'. Find frequency of the letter 'f'
1

Sentence: 'a glass vase sits between two statues'. Find frequency of the letter 'o'
1

Sentence: 'a large bear in a river with some rocks'. Find frequency of the letter 'e'

4