${}_{H_{2}O}=0\mathrm{.}997,t_{H_{2}O}=3\mathrm{.}91s$

$e_{\text{M}\text{e}\text{t}\text{h}\text{a}\text{n}\text{o}\text{l}}=0\mathrm{.}786,t_{\text{M}\text{e}\text{t}\text{h}\text{a}\text{n}\text{o}\text{l}}=3\mathrm{.}36s$

$e_{\text{E}\text{t}\text{h}\text{a}\text{n}\text{o}\text{l}}=0\mathrm{.}785,t_{\text{E}\text{t}\text{h}\text{a}\text{n}\text{o}\text{l}}=5\mathrm{.}47s$

If the viscosity of fluid $A$ is known to be ${}_A$ at a certain temperature, the absolute value of the viscosity ${}_{}$ of fluid $B$ can be obtained relatively by conducting an experiment on both fluids at that reference temperature. How can you obtain it and what is the value?

$($The reference liquid$($A$)$ was set to water.$)$

$2.$Why is the viscosity different for each sample?