a) The forward reaction is exothermic, hence when temperature is increased the equilibrium shift towards the reactants side to get rid of the excess energy. This will mean that more reactants are produced decreasing yield
b) There are a fewer number of moles of gas on the right side compared to the left side (Just count the coefficients before each compound) so a higher pressure will mean that the equilibrium will shift towards the products side in order to decrease the pressure. This will mean that more products are formed increasing yield
c) When something is powdered it's surface area to volume ratio increases. A higher surface area means that the particles around it have more area to work on so the frequency of collisions will increase increasing the rate of reaction. This is why iron is powdered.
