for polystyrene, the variation of viscosity with temperature follows the vogel$-$fulcher law with parameters b$=710$ and T$0=50$C$.$ plot the function $\{\backslash$displaystyle $\backslash$eta $\}/\{\backslash$displaystyle $\backslash$eta $\}0$ in the temperature range $80-150$C$.$ by what factor does the viscosity and relaxation time vary between the temperatures of $100$C and $140$C$?$