How do I remove this error while drawing a graph

ROOT
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  1. variable-sized object may not be initialized
    Float_t ex[n] = {.05,.1,.07,.07,.04,.05,.06,.07,.08,.05};

  2. use of undeclared identifier 'gr’
    gr->SetTitle(“TGraphErrors Example”);

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ROOT User’s Guide -> Graphs
Tutorials -> Graphs tutorials

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