C(m)=E[=]=E|x-2‖xm 5 C(m)-C2(m+1)-C2(m-1) m=±1 27/7 ( ) [ ] ( ) ( ) ( ) 1 1 2 2 5 0 4 5 1 1 1 1 1 4 2 2 2 0 k k m z k k m k k m x x x x x C m E z z E x x m C m C m C m m else − + − + + ⎡ ⎤ ⎛ ⎞⎛ ⎞ = = − − ⎢ ⎥ ⎜ ⎟⎜ ⎟ ⎣ ⎦ ⎝ ⎠⎝ ⎠ ⎧ = ⎪ ⎪ ⎪ = − + − − = ⎨− = 1 ⎪ ⎪ ⎪ ⎩ ±