Tablet PC Comparison provides a wide variety of information about tablet computers. Their website enables consumers easily compare different tablets using factors such as cost$,$ type of operating system, display size, battery life, and CPU manufacturer. A sample of $10$ tablet computers is shown below $($Tablet PC Comparison website$).$

$\backslash$table$[[$Tablet$,$Cost $($$$),\backslash$table$[[$Operating$],[$System$]],\backslash$table$[[$Display$],[$Size$],[($inches$)]],\backslash$table$[[$Battery$],[$Life$],[($hours$)]],\backslash$table$[[$CPU$],[$Manufacturer$]]],[$Acer Iconia W$510,599,$Windows,$10\mathrm{.}1,8\mathrm{.}5,$Intel$],[$Amazon Kindle Fire HD$,299,$Android,$8\mathrm{.}9,9,$TI OMAP$],[$Apple iPad $4,499,$iOS,$9\mathrm{.}7,11,$Apple$],[$HP Envy X$2,860,$Windows,$11\mathrm{.}6,8,$Intel$],[$Lenovo ThinkPad Tablet,$668,$Windows,$10\mathrm{.}1,10\mathrm{.}5,$Intel$],[$Microsoft Surface Pro,$899,$Windows,$10\mathrm{.}6,4,$Intel$],[$Motorola Droid XYboard,$530,$Android,$10\mathrm{.}1,9,$TI OMAP$],[$Samsung Ativ Smart PC$,590,$Windows,$11\mathrm{.}6,7,$Intel$],[$Samsung Galaxy Tab,$525,$Android,$10\mathrm{.}1,10,$Nvidia$],[$Sony Tablet S$,360,$Android,$9\mathrm{.}4,8,$Nvidia$]]$

a$.$ How many elements are in this data set?

b$.$ How many variables are in this data set?

c$.$ Which variables are categorical and which variables are quantitative?