Use MATLAB's fminbnd() function to find the maxima and minima of the following functions and graph the curves accordingly: a. f(x)=x+10x3 - 20x - 15 b. f(x)=(-0.5x) sin 2x c) Use the method of steepest descent MATLAB code to obtain the approximate position that makes fa f(x,x)=8x-20xx+17x-32x+40x Use relative minimum where (x1, x2) = (6, 4) as the starting point, As = 0.05, and 260 steps.