How To Use A Text Formula In A Real Formula

This is going to be hard to explain but, ill give it a try

I have a list of formula written in text in columnB
(-0.0045*x^3+0.2696*x^2-6.0587*x+100)/100
(-0.0045*(x*1.3)^3+0.2696*(x*1.3)^2-6.0587*(x*1.3)+100)/100
(-0.0045*(x*1.5)^3+0.2696*(x*1.5)^2-6.0587*(x*1.5)+100)/100
(-0.0045*(x*0.8)^3+0.2696*(x*0.8)^2-6.0587*(x*0.8)+100)/100
(-0.0045*(x*1.3)^3+0.2696*(x*1.3)^2-6.0587*(x*1.3)+100)/100
(-0.0045*(x*1.5)^3+0.2696*(x*1.5)^2-6.0587*(x*1.5)+100)/100

each formula correspond to a type of road in columnA
Rural Local
Rural Collector
Rural Arterial
Urban Local
Urban Collector
Urban Arterial

I would like to create a formula that will choose the right formula and substitute the variable "x" by a specific cell (lets put $Z$1) to finally give me the final answer in column C.