That's a very good question, sir.
When we started this project in 2010, we went to different people to look at what our choices were with models. We were also looking at the history of this particular fighter plane from the early 1990s to present day. We looked at more bottom-up, more detailed parameter models where you literally cost component by component—the engine, the airframe, stealth components, etc.—and then we looked at these cost-estimating relationship models.
We actually invested in proprietary models in both cases. We chose this one, sir, primarily because it looked like history was repeating itself in this case. The costs were providing significant overruns. Even when we were doing our work, already just in the research and development phase, there was already 60% cost overruns. It looked, in that sense, like history was repeating itself, and we became comfortable with this high-level estimate.
I repeat, to your very good first question, these are high-level models, and they should be complemented by the work of DND and other officials, more bottom-up detailed models.