In a simplified thermochemistry table, these reactions are listed. Treat lettered formulas such as MO or XCl2 as model compounds in a balanced symbolic system. (1) R(s) + 1/2 O2(g) -> RO(s), Delta H = -146 kJ; (2) RO(s) + 1/2 O2(g) -> RO2(s), Delta H = -90 kJ; (3) 2 R(s) + 3/2 O2(g) -> R2O3(s), Delta H = -392 kJ. Target: 1/2 O2(g) + R2O3(s) -> 2 RO2(s). Which expression shows the correct Hess's Law calculation?