Exer. $79-82:$ (a) Sketch the graph of $f$ on the given interval $[a, b] .$ (b) Estimate the range of $f$ on $[a, b] .$ (c) Estimate the intervals on which $f$ is increasing or is decreasing.
$$f(x)=x^{4}-0.4 x^{3}-0.8 x^{2}+0.2 x+0.1 ; \quad[-1,1]$$