The Standard Enthalpy of Formation of Gaseous Diborane, B₂H₆, Is

The standard enthalpy of formation of gaseous diborane, B₂H₆, is +31 kJ mol^-1 at 298 K. Use the following data for the molar heat capacities at constant pressure to determine the standard enthalpy of reaction at 450 K.
C_p,m^o / kJ mol^-1
B(s) 12.0
H₂(g) 28.8
B₂H₆(g) 56.4

A) +39 kJ mol^-1
B) +23 kJ mol^-1
C) +33 kJ mol^-1
D) +29 kJ mol^-1