Embarrassingly simple question that has me confused...

0 hi,
am practicing for an upcoming med math quiz and ran across a question re IV flow rates on this site (q #7) that has me confused..Here it is:
7. Your patient has an order to receive 800 units of Heparin per hour by continuous intravenous infusion. If the pharmacy mixes the IV bag to contain a total of 5,000 units of Heparin in 500 ml of D5W, how many cc's per minute should the patient receive?
The answer they give is 80 cc's/minute...
But, wouldn't that give the pt 800 units Heparin per minute?
The answer I came up with is: 1.3 ml/minute. here's how: 5,000 units per 500 ml = 10 units per ml.
800 units per hour divided by 60 minutes=13.3 Units per minute. so, 1.3ml per minute = 13.3 units per minute x 60 minutes per hour =798 units per hour.
feel like I am missing something obvious. or the site is wrong. I vote the latter.
thanks for the help.
(any way to post this anonymously) 

Dec 25, '10 by BCRNATheir answer is wrong if it is 80 cc/minute. That would be 4800 cc per hour, giving someone 5 liters per hour could put them in serious overload, not to mention it would have 48000 units of heparin. That is enough to go on cardiopulmonary bypass.
Answer should be 80 cc/hour. Your answer would be very close, giving 1.3 cc per minute would be 780 cc per hour (total of 780 units). Difference is just from rounding, actual per minute is 1.333......
Should always check heparin dose with another nurse, and use some common sense when you see that an extreme amount of fluid or dosages are given. 
Dec 25, '10 by BCRNAYou did a really good thing by asking by the way. Patients have been hurt by nurses to afraid ask.

Dec 26, '10 by soxfan80I got 1.33ml/min
800units/hour = 13.3 units/min
ml 500ml 13.3 units 6650
___ = _____ x _________ = _____
min 5000units 1 min 5000 
Dec 26, '10 by soxfan80I got 1.33 ml/min
800units/hour =13.3units/min
ml 500ml 13.3units 6650
_____ ______ x ________ =_______
min 5000units 1 min 5000 