line 20 3a21 3a 27store 27 is not defined no undef redux

1import { createStore } from "redux";
2const store = createStore(reducer);
3 ReactDOM.render(
4   <Provider store={store}>
5     <MuiThemeProvider theme={theme}>
6       <App />
7     </MuiThemeProvider>
8   </Provider>,
9   document.getElementById('root')
10 );
11//here reducer is reducer function