Can someone help me out with this chemistry question?

[Andrew G]

For the system 2SO2(g) + O2(g) <==> 2SO3(g), ?H is negative for the production of SO3. Assume that one has an equilibrium mixture of these substances. Predict the effect of each of the following changes on the value of the equilibrium constant and on the number of moles of SO3 present in the mixture at equilibrium. Briefly account for each of your predictions. (Assume that in each case all other factors remain constant.)

a) Decreasing the volume of the system.
b) Adding oxygen to the equilibrium mixture
c) Raising the temperature of the system

Please help me out and thank you in advance

(PS: If it says ?H is negative for the production of SO3, does that mean the reaction is exothermic in the forward reaction?)