The diagram below shows the market demand ($D$) curve and two supply ($S_1$ and $S_2$) curves for a premium brand of organic blueberries, sold in 250g packs.

Following the imposition of an import tariff, consumption falls from 600,000 packs per week to 540,000 packs per week.

If the price elasticity of demand for this brand of organic blueberries is -0.8, the price must have increased by: