import numpy as np

# Rows: roof A and roof B. Columns: three days.
litres = np.array([[12, 18, 24], [6, 9, 15]], dtype=np.int64)
print(litres.ndim, litres.shape, litres.size)
print(litres.sum(axis=0).tolist())
print(litres.sum(axis=1).tolist())