Automatic temperature controller

[MrP]

Hello!

I'm having some trouble analysing this automatic temperature controller circuit. Can you please give me some indications? Thank you so much!

[img]http://i39.tinypic.com/rtfd3b.jpg[/img]

How can I find the resistor RA value to impose a 45ºC temperature on resistor R5?
When switches I1 and I2 are open, how can I find the current that will start to heat the resistor R5 and the power dissipated?
And how can I find the same current with only one of the switches open?

I just need some advice to analyse this. Thank you so, so much!