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

Sentence: 'a girl sits on a surfboard and smiles'. Find frequency of the letter 'i'
3

Sentence: 'a mixed bouquet of flowers in a glass vase set before a window'. Find frequency of the letter 'w'
3

Sentence: 'five skiers pose with their skis next to them'. Find frequency of the letter 'm'

1