A delivery agent delivers goods to four stores and then returns to the warehouse. The driver delivers 1/4 of the load to the 1st store, then 1/2 of the remainder at the next store, then 1/4 of the remainder at the 3rd store and 1/3 of what is left to the 4th store. The agent has 480 units of goods to go back to the warehouse. How many units of goods did he deliver?