As for their relative elasticities, we can compare how much of the tax is being "paid" by each side of the market. Out of the total tax of $12, consumers are paying 31 - 25 = 6 (where we are comparing the prices paid/received after tax with the original price), while sellers are receiving 25 - 19 = 6. The more elastic side is the one who pays a smaller share of the tax burden.