The overall chemical equation is C(s)+H2O(g)->CO(g)+H2(g). To calculate the final enthalpy of the overall chemical equation, which step must occur?

a)Reverse the first equation, and change the sign of the enthalpy. Then, add.

b)Reverse the second equation, and change the sign of the enthalpy. Then, add.

c)Multiply the first equation by three, and triple the enthalpy. Then, add.

d)Divide the third equation by two, and double the enthalpy. Then, add.