Mode = ?
(a) xk + h \(\{\cfrac{f_{k-1}-f_k}{2f_k-f_{k-1}-f_{k+1}}\}\)
(b) xk + h \(\{\cfrac{f_{k-1}-f_{k-1}}{2f_k-f_{k-1}-f_{k+1}}\}\)
(c) xk + h \(\{\cfrac{f_k-f_{k-1}}{f_k-2f_{k-1}-f_{k+1}}\}\)
(d) xk + h \(\{\cfrac{f_k-f_{k-1}}{f_k-f_{k-1}-2f_{k+1}}\}\)