= Solution
\b[The descending line is $^3T_{1g}(F)$; the low rising line is $^3T_{2g}$; the steep line is $^3A_{2g}$; and the branch starting at $15B$ is $^3T_{1g}(P)$.] Their high-field slopes, in the same order, are
$$
\boxed{-\frac45,\quad\frac15,\quad\frac65,\quad\frac15.}
$$
These are slopes of the supplied absolute term energies relative to their chosen reference, not slopes of transition energies measured upward from the ground state. The two $T_{1g}$ states share a <symmetry> and mix, whereas the crossing of $A_{2g}$ and the upper $T_{1g}$ branch is allowed because they have different <irreducible representations>.
\Image[/past-exam-of-the-chemistry-course-of-the-year-3-of-the-natural-sciences-course-of-the-university-of-cambridge/2021/paper-2a-orgel.png]
{title=Triplet crystal-field energies and their strong-field slopes}
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