某同学利用如图所示的装置测量滑轮组的机械效率．他用F=10N的拉力将重为17N的物体匀速提升0.2m．在这一过程中，他做的总功为 ____J，滑轮组机械效率为 ____

                                                                                                    山居秋暝
                                                                                                      王　维
                                                                                        空山新雨后，天气晚来秋。
                                                                                        明月松间照，清泉石上流。
                                                                                        竹喧归浣女，莲动下渔舟。
                                                                                        随意春芳歇，王孙自可留。