Here mass is floating on the piston at equilibrium
So it will have constant pressure always remains constant
So final pressure is same as initial pressure = 900 kPa
now we can say



so final pressure is 900 kPa and final volume is 1.14 m^3
Answer: The force constant of the spring is 116.1N/m
Explanation: Please see the attachments below
I’m guessing convection currents since you mention mantle and core, reminds me of heat
The suns incoming rays are perpendicular to the Tropic of Capricorn