The Cathay interview book that these questions come from is not completely correct . There are a few errors in it here and there. Like the answer to your question #4. The book gives the answer as -20c.
Old Smokey, I have learned an enormous amount from you on these forums, and for that I thank you. But with reference to #1 is it not closer to 9556ft?
My math for that goes like this.
OAT is ISA -15, using 4% per 10deg, we use 6% of the indicated altitude minus the station elevation.
10000ft-2500ft=7500ft
6% of 7500ft is roughly 450ft.
10000-450=9550.........
Have I been doing this wrong?
If I could ask for your workings on how you get your answer it would ease my confusion!