Answer:
Cost of inventory= $1,250
Step-by-step explanation:
Giving the following information: 
Beginning inventory 10 units at $55 
First purchase 25 units at $60 
Second purchase 30 units at $65 
Third purchase 15 units at $70 
The firm uses the periodic inventory system. 
During the year, 60 units of the item were sold. 
Units in inventory= 80 units - 60 units= 20 units
Average cost= (55 + 60 + 65 + 70)/4= $62.5
Cost of inventory= 20*62.5= $1,250