Answer:
The amount of drug left in his body at 7:00 pm is 315.7 mg.
Explanation:
First, we need to find the amount of drug in the body at 90 min by using the exponential decay equation:

Where:
λ: is the decay constant = 
: is the half-life of the drug = 3.5 h
N(t): is the quantity of the drug at time t
N₀: is the initial quantity
After 90 min and before he takes the other 200 mg pill, we have:

Now, at 7:00 pm we have:

Therefore, the amount of drug left in his body at 7:00 pm is 315.7 mg (from an initial amount of 400 mg).
I hope it helps you!
Answer:
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Explanation:
Answer:
Mass, temperature, and phase.
I think temperature because the higher the temperature of a given quantity of a substance, more is its thermal energy. Similarly, for the same temperature, higher mass of a substance will contain more thermal energy.
To separate off different products in order of their boiling points. You do it by a process of heating and cooling in a horizontal condenser usually.