The following rates would be required to meet the cash flow target discount at 7.5%  to cover the capital cost.

15 Yr      10,000 MMBtu/d    @    $.297
10 Yr      10,000 MMBtu/d    @    $.37
  5 Yr      10,000 MMBtu/d    @    $.62
  1 Yr      10,000 MMBtu/d    @  $2.71

The following rates would be required on the remaining capacity to achieve a 15% IRR for the project.

15 Yr    @  $.33  assumes no fuel tracker.
15 Yr    @  $.36  assumes a fuel tracker starting in year 6.

I will be on vacation tommorrow, but if you want some additional cases ran on Monday, please send me an email and I will start working on them first thing Monday morning.

Thanks,
James