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

Sentence: 'a birthday cake with a number one and three candle'. Find frequency of the letter 'w'
1

Sentence: 'a girl laying on a bed posing for a picture'. Find frequency of the letter 'i'
4

Sentence: 'there is a man riding his skate board at the skate park'. Find frequency of the letter 'a'

7