The Following Information Regarding the Ten Richest Americans Was Reported

The following information regarding the ten richest Americans was reported in a recent issue of Forbes.
$\begin{array}{|l|c|c|c|l|l|}\hline \text { Name }&\text { Ranking } & \begin{array}{c}\text { Worth } \\\text { \$Billions) }\end{array} & \text { Age } & \begin{array}{c}\text { Marital } \\\text { Status }\end{array} & \text { Source } \\\hline \text { Gates, William } & 1 & 72.0 & 51 & \text { married } & \text { Microso } \\\hline \text { Buffett, Warren } & 2 & 52.0 & 77 & \text { married } & \text { Berkshire Hathaway } \\\hline \text { Adelson, Sheldon } & 3 & 28.0 & 74 & \text { married } & \text { casinos, hotels } \\\hline \text { Ellison, L. J. } & 4 & 26.0 & 63 & \text { married } & \text { Oracle } \\\hline \text { Brin, Sergey } & 5 & 18.5 & 34 & \text { married } & \text { Google } \\\hline \text { Page, Larry } & 5 & 18.5 & 34 & \text { single } & \text { Google } \\\hline \text { Kerkorian, Kirk } & 7 & 18.0 & 90 & \text { divorced } & \text { investments, casinos } \\\hline \text { Dell, Michael } & 8 & 17.2 & 42 & \text { married } & \text { Dell } \\\hline \text { Koch, Charles } & 9 & 17.0 & 71 & \text { married } & \text { oil, commodities } \\\hline \text { Koch, David } & 9 & 17.0 & 67 & \text { married } & \text { oil, commodities } \\\hline\end{array}$
a. How many elements are in the above data set?
b. How many variables are in this data set?
c. How many observations are in this data set?
d. Which variables are categorical and which are quantitative?
e. What measurement scale is used for each variable?