23. SEGMENT REPORTING The Groups chief operating decision maker has been identified as the Chief Executive Officer who reviews U.S. GAAP financial information of its operating segments when making decisions about allocating resources and assessing the performance of the Group. The Group identified three operation segments, including professional education services, business start-up training services and the sale s of learning simulation software during the years ended September 30, 201 8 and 201 9 . The Group operates primarily in the PRC and substantially all of the Groups long-lived assets are located in the PRC. The Groups chief operating decision maker evaluates performance based on each reporting segments net revenue s , operating costs and expenses, and operating income. Net revenues, operating costs and expenses, operating income, and total assets by segment were as follows: Year s ended September 30, 2017 2018 2019 US$ US$ US$ Net revenues 130,988 166,668 211,822 Professional education services 114,190 150,484 196,047 Business start-up training services 5,276 4,608 2,796 Sale s of learning simulation software 11,522 11,576 12,979 Operating costs and expenses: Cost of sales (57,412 ) (87,883 ) (104,741 ) Professional education services (50,168 ) (79,168 ) (96,044 ) Business start-up training services (2,069 ) (2,644 ) (1,777 ) Sale s of learning simulation software (5,175 ) (6,071 ) (6,920 ) Selling and marketing (34,910 ) (44,717 ) (61,460 ) Professional education services (30,696 ) (39,698 ) (56,334 ) Business start-up training services (869 ) (1,127 ) (1,226 ) Sale s of learning simulation software (3,345 ) (3,892 ) (3,900 ) General and administrative (15,955 ) (16,760 ) (20,064 ) Professional education services (12,890 ) (14,548 ) (16,745 ) Business start-up training services (1,034 ) (896 ) (1,930 ) Sale s of learning simulation software (2,031 ) (1,316 ) (1,389 ) Impairment of goodwill   (1,517 ) Business start-up training services   (1,517 ) Unallocated corporate expenses (3,513 ) (4,493 ) (4,855 ) Total operating costs and expenses (111,790 ) (153,853 ) (192,637 ) Professional education services (93,754 ) (133,414 ) (169,123 ) Business start-up training services (3,972 ) (4,667 ) (6,450 ) Sale s of learning simulation software (10,551 ) (11,279 ) (12,209 ) Unallocated corporate expenses (3,513 ) (4,493 ) (4,855 ) Other operating income 1,912 3,051 2,968 Professional education services 184 643 1,053 Business start-up training services 91 76 102 Sale s of learning simulation software 1,637 2,332 1,813 Operating income (loss) 21,110 15,950 22,848 Professional education services 20,620 17,797 28,672 Business start-up training services 1,395 17 (3,552 ) Sale s of learning simulation software 2,608 2,629 2,583 Unallocated corporate expenses (3,513 ) (4,493 ) (4,855 ) Segment assets 224,551 328,925 355,350 Professional education services 133,836 236,496 273,005 Business start-up training services 45,569 46,205 36,735 Sale s of learning simulation software 45,146 46,224 45,610 Total assets 224,551 328,925 355,350 Amortization and depreciation 4,790 6,299 12,723 Professional education services 3,001 4,479 10,939 Business start-up training services 36 36 69 Sale s of learning simulation software 1,753 1,784 1,715 (Loss) gain from equity method investments (153 ) (172 ) (1,484 ) Professional education services (153 ) 58 (1,173 ) Business start-up training services  (230 ) (311 ) Sale s of learning simulation software