Let's order the four actions in order in which they should be done:
d. Identify the unresolved problem or dilemma.
a. Determine the desired outcome.
b. Propose a possible solution.
c. Act on a possible solution.
Notice how the different steps depend on the previous steps, for example you can only act on the possible solution, once you know what the solution is.
So the first step will be d. Identify the unresolved problem or dilemma.