instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a girl sits on a surfboard and smiles'. Find frequency of the letter 'i'
answer:
3


question:
Sentence: 'two people holding their skies in a snowy resort'. Find frequency of the letter 'n'
answer:
3


question:
Sentence: 'an avocado, an apple, a banana, a pear, and an orange'. Find frequency of the letter 'a'
answer:

14