The responses of a sample of 1000 adults who were asked what type of corrective lenses they wore are shown in the table at the left.

Type of lenses                                    Frequency, f

Contacts ………………...........………………..        40

Eyeglasses ……………..........…………………      570

Contacts and eyeglasses ……...…………..      180

None …………………............……….…………      210

Find the mean, the median, and the mode of the data, if possible. If any measure cannot be found or does not represent the center of the data, explain why.