Electronics homework

[CHRIS_18]

Guys I could really use some help with the last part of my homework...The problem is that I cannot find the details about Θ h.s and Θamb.....I have upload photos below.

 

[Arouse1973]

I think you will find you choose them as part of your design. So it's the temperature of the heat sink you can tolerate that will determine its size. And ambient well say 25 degrees and a temp of 50 degrees on the heat sink, these are just examples mind.
Thanks
Adam