Calculate the viscosity of the gas mixture given below at $200F$ and a pressure of one atmosphere absolute$.$

$\backslash$table$[[$Component$,\backslash$table$[[$Composition$],[($mole fraction$)]]],[$Methane$,0\mathrm{.}850],[$Ethane$,0\mathrm{.}090],[$Propane$,0\mathrm{.}040],[$n$-$Butane,$0\mathrm{.}020],[,1\mathrm{.}000]]$