In this task, you need to reverse all words of a given length in the sentence. The number of letters in a word determine its length. For example, the length of the word "apple" is 5.

Example Input: Sentence: 'a bathroom with a white bath tub under a mirror'. Reverse all words of length '5' in the given sentence.
Example Output: a bathroom with a etihw bath tub rednu a mirror

Example Input: Sentence: 'an assortment of chinese dinner options are arranged'. Reverse all words of length '8' in the given sentence.
Example Output: an assortment of chinese dinner options are degnarra

Example Input: Sentence: 'a bench mounted high up on a mountain'. Reverse all words of length '4' in the given sentence.
Example Output:
a bench mounted hgih up on a mountain