Re-order paragraphs

b) Researchers have developed a system that can 3-D print the basic structure of an entire building.

c) Structures built with this system could be produced faster and less expensively than traditional construction methods allow.

a) Even the internal structure could be modified in new ways; different materials could be incorporated as the process goes along.

d) Ultimately, the researchers say, this approach could enable the design and construction of new kinds of buildings that would not be feasible with traditional building methods.