thermodynamics course ( solve for both with good explaination)

P3: Find the change in specific internal energy for carbon dioxide between 600K and 1200K for a constant specific heat value at room temperature. a) 291.8kJ/kg b) 391.8kJ/kg c) 491.8k/kg d) 591.8kJ/kg P4: Air is compressed in a polytropic process from 325K,125kPa to 500K,300kPa. The specific work for this process is: a) 51.8k/kg b) 61.8kJ/kg c) 71.8kJ/kg d) 81.8kJ/kg