Please help me to understand this problem:

The lengths of plate glass parts are measured to the nearest tenth of a millimeter. The lengths are uniformlyr distributed with values at every tenth of a millimeter sterling at 590.0, and continuing through 590.9. Determine the mean and variance of le lengths. (a) mean {in tenths of millimeters) Round your answerto two decimal places (e.g. 93.76}. (b) variance (in tenths of millimeter-.32) Round your answer to three decimal places (e.g. 93.?65). ia E [by