During a quality assurance check, the actual weights (in kilograms) of eight sacks of cement were recorded as 20.5, 19.4, 19.6, 18.0, 21.0, 20.2, 20.4, and 20.9.

(a) Find the mean and the median of the contents.

(b) The fifth value was incorrectly measured and is actually 20.0. Find the mean and the median of the contents again.

(c) Which measure of central tendency, the mean or the median, was affected more by the data entry error?