For the year ended December 31
2017
2016
2015
$ millions
Selling, transport and marketing expenses
Transport
497
475
417
Cost of labor
122
119
113
Other
127
128
123
746
722
653
General and administrative expenses
170
188
150
Professional Services
49
77
103
42
56
97
261
321
350
Research and development expenses, net
40
48
54
15
25
20
55
73
74