In this task, you need to count the number of times the given letter appears in the given sentence.
One example: Sentence: 'a large group of bananas proped up on several bicycles'. Find frequency of the letter 'e'
Solution is here: 5
Explanation: The letter 'e' appears 5 times in the sentence.

Now, solve this: Sentence: 'in the background, a shaded blue mountain and soft blue sky, fronted by a boat on water, leads to a foregrounds of water spry and a big wave, bearing a man in a rolled up top and trunks, hunched over and riding a surf board'. Find frequency of the letter 'r'
Solution:
14