Sales Example                              1

                       Obs    city            sales

                         1    Chicago         54062
                         2    Atlanta         41747
                         3    Los Angeles    107998
                         4    Seattle         32769
                         5    Houston         67761
                         6    Chicago         68285
                         7    Denver          91617
                         8    Boston          14488
                         9    Houston         82615
                        10    Seattle         43140
                        11    Denver          56386
                        12    Chicago         42918
                        13    Chicago        114755
                        14    Houston         99244
                        15    Denver          38818
                        16    Seattle         21904
                        17    Houston        109475
                        18    Los Angeles     66452
                        19    Miami           34250
                        20    Denver          72495
                        21    Houston         72379
                        22    Chicago         35163
                        23    Denver          92795
                        24    Seattle         84689
                        25    Chicago         40565
                        26    Los Angeles      7026