KöMaL 2023 K785

In the shops of three merchants Ali, Selim and Khafim a barrel of olives had the same price at the beginning of June. Ali increased the price by 10%, then by 10% again, and then at the beginning of September decreased the price by 20%. Selim increased the price by 20%, then decreased it by 10%, and then at the beginning of September decreased it by 10% again. Khafim increased the price by 20%, and then at the beginning of September decreased it by 20%. We know that at the beginning of September Ali sold a barrel of Olives 4 dinars cheaper than Selim. How much did a barrel of olives cost at the beginning of September in Khafim's shop?