First, to compute the mean value we use the following formula:

The mean is 167.
To find the median we order the numbers from lowest to highest: 15, 65, 75, 90, 95, 110, 140, 185, 195, 215, 250, 255, 260, 270, 285.
The median of the data set is 185.
Finally, notice that no number is repeated so there is no mode. The answer is DNE.