Answer:
48 M3/kg.
Step-by-step explanation:
The predicted energy density of ethane can be calculated by taking the average of the energy densities of methane and propane, since ethane has a chemical composition that falls between these two fuels. Thus, the predicted energy density of ethane is (50+47)/2 = 48.5 MJ/kg, which is closest to 48 M3/kg.