In Destiny, completing a Weekly Nightfall Strike awards you a buff for the remainder of the week called "Radiant Light". Radiant Light increases all experience and reputation gained on the character that cleared the Nightfall Strike by 25% until the next Tuesday reset. Recently, there has been a promotion with Red Bull where you can earn an item (Focused Light), which increases experience gained by 50% for 30 minutes.
Do these experience bonuses stack? And, if so, do they stack multiplicative manner (e.g. 1.5 * 1.25 = 1.875) or additive manner (e.g. 0.5 + 0.25 + 1 = 1.75)?