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

Sentence: 'a man riding a skateboard up the side of a ramp'. Find frequency of the letter 'u'
1

Sentence: 'a few men walking through a market place'. Find frequency of the letter 'f'
1

Sentence: 'a boy catching a frisbee while standing ins bunch of leaves'. Find frequency of the letter 'a'

5