Sufficient funds are available to build up to four stories on a building site. The projected costs and revenues of having either $1,2,3$ or $4$ floors is tabled below. The investment life is $20$ years with a minimum attractive rate of return at $15\%.$ How many floors should be erected for this building?

$\backslash$table$[[\backslash$table$[[$Number of$],[$Stories$]],$Total Cost,$\backslash$table$[[$Operating$],[$Cost per year$]],\backslash$table$[[$Total Revenue$],[$per year$]]],[1,1\mathrm{.}7,0\mathrm{.}38,0\mathrm{.}58],[2,2\mathrm{.}7,0\mathrm{.}88,1\mathrm{.}33],[3,3\mathrm{.}6,1\mathrm{.}40,1\mathrm{.}95],[4,4\mathrm{.}7,1\mathrm{.}90,2\mathrm{.}70]]$