8. Find all second-order derivatives of each of the following functions. Then, for each function, use its second derivatives to determine whether the function is convex at all points in its domain, concave at all points in its domain, or neither. a. y=f(x)='/(1+x2); xEIR b. 2 = f(x,y) = 3x4 + 5x2yy3; (x,y) E R2 c. z=f(x,y)=5x2y2+2xy+6x+2y+7 (x,y)EIlR2