Question 12 5 pts Consider combustion of coal in pure oxygen (oxycombustion) and in air. The percent theoretical oxidizer in each case is 100%. Which case will have a higher adiabatic flame temperature? O Combustion in pure oxygen O They will be the same Combustion in air O Not enough information Question 13 5 pts A water heater burns 3 kg of natural gas to heat a tank containing 300 kg water from 20C to 80 Assume the water has a constant specific heat of 4.0 kJ/kg-K, and that the lower heating value of natural gas is 47 MJ/kg. a What is the combustion efficiency of this water heater (based on LHV)? Enter your answer as a percent (e.g., 50, not 0.5, for 50%)