In baking cookies, the order in which you add ingredients generally does not affect the total mass of the cookie batter. According to the law of conservation of mass, matter cannot be created or destroyed, so the total mass of the batter is simply the sum of the masses of all the individual ingredients, regardless of the order in which they are combined.
As for the combined mass of the first coin and the third coin, you would need to provide the specific masses of those coins in order to calculate their combined mass. Please provide those values, and I'd be happy to help with the calculation!