Dose - Caffeine dose for a productive boost, not a jittery fuckabout

[Akewstick]

I've searched, couldn't find anything, sorry if this has been covered.

Stevie Boldank should have been writing an essay for the past 2 days. Thursday he decided he would give himself a break and have a drink with a friend, "a drink" turned into 1.5 litres of 40% vodka between the two of them. Stevie went to sleep at 8am, was woken up by the alarm clock he had set at 11, so he could start work, but was still really drunk and felt like absoloute shit. So Stevie met up with another friend and they smoked an amount of weed he's pretty sure was monstrously large, got home at 8pm, fell asleep at about 10, and slept for faaar too long.

The essay is unstarted, and Stevie is probably a bit fucked, he's on 300mg of caffeine (pills, orally), he's never tried it in any form other than coffee and red bull and all that shit before (and snorting some lines of it when he was 16), so what he'd like to know is this:

How high can you take the dose of caffeine before it ceases to make you productive, and makes you unable to sit down, so you walk around and think about the details that you've noticed in the subject of what makes certain frying pans non-stick, that you never knew existed before. SWIM used to use speed to get work done, and has quite often taken the dosage too high and then discovered that he's on a main road in the dark with his headphones on because he felt the compulsion, and the work he was supposed to be doing hasn't entered his head for hours.