Answer:
 $480,000
Step-by-step explanation:
The computation of the total manufacturing costs for Job No. 305 is shown below:
= Direct material cost + direct labor cost + manufacturing overhead cost 
where, 
Direct material cost = $180,000
Direct labor cost is 
= $200,000 ÷ 200% × 100%
= $100,000
And, the manufacturing overhead cost is $200,000
So, the total manufacturing overhead is 
= $180,000 + $100,000 + $200,000
= $480,000