Write a user-defined function with function call \(s=\operatorname{speed} c a l c(x, t 0)\) that calculates the speed of a moving object, whose position is described by a symbolic function \(\mathrm{x}\), at a specified time \(t 0\). Execute the function to find the speed ( \(\mathrm{at} t=2.5\) ) of an object whose position is described by \(x(t)=0.75 t^{3}-2 t^{2}+1.4\).