Sulfur has two solid forms - a (or rhombic) and b (or monoclinic). The standard enthalpies of combustion, in which the product is SO2, are -296.53 kJ/mol for S(s,a) and -296.86 kJ/mol for S(s,b) a 298 K. Find the standard reaction enthalpy for the process S(s,a) -> S(s,b) at 298 K.