Each year, Forbes magazine compiles a list of the 400 richest Americans. As of September 19, 2012, the top 10 on the list are as shown in the following table.

Person Wealth ($ billions)

Bill Gates ..............66.0

Warren Buffett ..............46.0

Larry Ellison ................41.0

Charles Koch ................31.0

David Koch.................31.0

Christy Walton & family .....27.9

Jim Walton ................26.8

Alice Walton ................26.3

S. Robson Walton ............26.1

Michael Bloomberg ..........25.0

Find the

a. Mean.

b. Median.

c. Mode(s).

For the mean and the median, round each answer to one more decimal place than that used for the observations.