Number of oranges, apples and bananas sold by the shopkeeper are in the x, y and z respectively. Price of each orange , each apple and  each banana are in the ratio 2: 3: 1.Total cost of half of the sold oranges and 60% of the sold apples are Rs. 156. If the number of oranges sold is 6 less than apples sold and the number of apples sold is 6 less than the bananas sold. Total selling cost of bananas is Rs. 72. Find how many dozens of oranges sold.