Does it take energy for polymerization reasctions to proceed or ddo they occur spontaneoulsly?? Why or why not??

Question

http://en.wikipedia.org/wiki/Endothermic_reaction

10. From a bottle of molten nutrient agar you need to pour 20 agar plates each containing 50 mg ml-1 ampicillin. Each plate will contain ~ 25ml of nutrient agar, and you have a stock ampicillin antibiotic solution of 200 mg ml-1. What volume of ampicillin stock solution do you need to add to the bottle of molten agar before pouring the plates? 

help :P