\text { Let } f: \mathbf{R} \rightarrow \mathbf{R}, f(x)=e^{-x^{2}} \text {. Find } an open set DCR such that f(D) is not open;a (b)a closed set FCR such that f(F) is not closed; (c) a set A CR such that f(A) # f(A).

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