Consider the function $f(x,y)=-x^3+6xy-4y^2+9.$

Which of the following statements is true. $..$

$...f(1\mathrm{.}5,1\mathrm{.}125)$ is a relative maximum value.

$...(1\mathrm{.}5,1\mathrm{.}125,17\mathrm{.}4375)$ is a saddle point on the graph $z=f(x,y).$

dotsf$(1\mathrm{.}5,-1\mathrm{.}125)$ is a relative minimum value.

dotsf$(1\mathrm{.}5,-1\mathrm{.}125)$ is a relative maximum value.