$[5$ marks$]$ The function $f(x)=e^{3x}-e^{-3x}$ has been interpolated at the nodes at $(-1,0,1)$ using

Vandermonde matrix method. Evaluate the upper bound of the interpolation error for the interval

$-1\mathrm{.}5,1\mathrm{.}5$ using Cauchy's theorem. Keep up to $4$ significant figures.