Generate random and unique probabilities based on the data in a column rstudio

I have a database with different ages (16-85) what I'm triying to do is to assign a random probability to each age but following the next conditions:

1. The random probability show be between 20-100
2. The probability show be higher in the lowest and higest values

For example: I have this dataframe

Age	Probability
16	85
18	80
25	70
30	50
35	40
65	60
75	65
85	70

I'd really appreciate if you can help me with this. Tank you so much!