The graph of a function f consists of three straight-line segments joining the points (−6,0) to (−2,4), then (−2,4) to (1,1), and finally (1,1) to (5,5). Which of the following piecewise functions could represent f′?
a) f′(x)=⎩⎨⎧4,−3,4,−6<x<−2,−2<x<1,1<x<5.
b) f′(x)=⎩⎨⎧1,0,1,−6<x<−2,−2<x<1,1<x<5.
c) f′(x)=⎩⎨⎧1,−1,1,−6<x<−2,−2<x<1,1<x<5.
d) f′(x)=⎩⎨⎧−1,1,−1,−6<x<−2,−2<x<1,1<x<5.