You quoted $5.10 as the total spread you would pay.

So:  $6 + $5.1 = $11.10

Question:  What is the credit you will give Pasadena time their capactiy of 
3886 MMBtu/d?

Answer:
To figure out what you are paying for the capacity:

Assume SJ Index = 6.00

Then, 
Basin Price/(1 - Fuel %) + Variable Cost + Demand Charge (Kim's # for 
Pasadena) = Border Index

Demand Charge = Border Index - $.026 - (Basin Price/(1- .0388)) 

x = 11.10 - .026 - 6.00/(.9612)

11.10 - .0266 - 6.2422

$4.83 is the implied demand charge 

$4.83 * 3,886 * 29 = Total Credit 

Chris