We used a combination of comparators. We used ships that were of a roughly similar size but not with the same mission. We also looked at ships with a similar mission but not of a similar size.
There could have been ships of broadly the same size and the same mission that we could have used, but these were Russian-made ships, so we didn't think there would be sufficiently good data to provide a reasonable estimate.
Therefore, we took ships of a similar size, different mission; and same mission, different size. We also looked at the historical costs for the Arctic offshore patrol ships and the joint support ships. Combining all these factors, we arrived at a cost estimate for the polar icebreakers. Chris and Eskandar would be happy to provide you more details if you are interested in having more details as to how we included each and every one of these cost comparators into our model.