(1) This section applies if a person is charged with a single offence against this chapter that involves—
(a) trafficking in 2 or more kinds of controlled drug; or
(b) manufacturing 2 or more kinds of controlled drug; or
(c) selling 2 or more kinds of controlled precursor; or
(d) manufacturing 2 or more kinds of controlled precursor; or
(e) possessing 2 or more kinds of controlled precursor; or
(f) cultivating 2 or more kinds of controlled plant; or
(g) selling 2 or more kinds of controlled plant; or
(h) supplying 2 or more kinds of controlled drug to a child.
(2) In a prosecution for the single offence—
(a) the quantity of drugs or plants is a trafficable quantity if the total of the required fractions of the trafficable quantity of each of the drugs or plants is 1 or more; or
(b) the quantity of drugs, precursors or plants is a commercial quantity if the total of the required fractions of the commercial quantity of each of the drugs, precursors or plants is 1 or more; or
(c) the quantity of drugs, precursors or plants is a large commercial quantity if the total of the required fractions of the large commercial quantity of each of the drugs, precursors or plants is 1 or more.
(3) In this section, the required fraction of—
(a) a trafficable quantity of a drug or plant is the actual quantity of the drug or plant divided by the smallest trafficable quantity of the drug or plant; and
(b) a commercial quantity of a controlled drug, precursor or plant is the actual quantity of the drug, precursor or plant divided by the smallest commercial quantity of the drug, precursor or plant; and
(c) a large commercial quantity of a controlled drug, precursor or plant is the actual quantity of the drug, precursor or plant divided by the smallest large commercial quantity of the drug, precursor or plant.
(4) For a trafficable, commercial or large commercial quantity of a controlled drug—
(a) the required fraction must be worked out on the basis of quantities of the drug in pure form; and
(b) the required fraction is zero if—
(i) a regulation does not prescribe a trafficable, commercial or large commercial quantity of the controlled drug; or
(ii) a regulation prescribes a trafficable, commercial or large commercial quantity for a mixture of substances containing the controlled drug but not for the drug in pure form; or
(iii) a regulation prescribes different forms of the controlled drug by reference to the percentage of a particular substance in the drug.