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

Sentence: 'a river with a long dragon boat in it and rowers on the boat in sets of two, along with two other people'. Find frequency of the letter 'h'
4

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

Sentence: 'a surfer riding a wave in the ocean'. Find frequency of the letter 'n'

3