Weighted Impurity of a Split

A node holds 80 rows, 40 positive and 40 negative. A candidate split sends 60 rows left (36 positive, 24 negative) and 20 rows right (4 positive, 16 negative). scikit-learn scores a split with

$G(Q_m, \theta) = \frac{n^{left}_m}{n_m} H(Q^{left}_m) + \frac{n^{right}$m}{n_m} H(Q^{right}m), \qquad H(Q_m) = \sum_k p{mk}(1 - p{mk})

What is the parent's Gini impurity and the weighted Gini of the split?