Use MATLAB's fminbnd() function to find the maxima and minima of the following functions and graph the curves accordingly: a. f(x) = x4 + 10x3 - 20x - 15 b. f(x) = e(-0.5x) sin 2x c) Use the method of steepest descent MATLAB code to obtain the approximate position that makes fa relative minimum where f(x,x)=8x7 20xx +17% 32x + 40x Use (x1, x2) = (6,4) as the starting point, As = 0.05, and 260 steps