this is how they are figuring out the problem. 250 ml _____ 800 mg you have to divide this to find out the mcg: when you divide you come out with 3.2 to convert to mcg you must add three zero's> 3200 mcg. Then you convert the weight to kg. 150 lbs divided by 2.2 Now you can plug your numbers in. 5 ml X 3200 mcg ______________ 60 min. X 68.18 equals: 16000 ------- 4090.8 answer: 3.92 hope that helps.