Final answer:
The total cost of (Option a) Job 56 would decrease if no engineering hours were required, as the cost allocated for engineering design would be removed from the job costing.
Step-by-step explanation:
If Job 56 required no engineering hours, its total cost would decrease. The cost associated with engineering design is an element of job costing. Since there are no engineering hours required for Job 56, the $900 allocated for engineering design would not be applied, thereby reducing the overhead. The costs for direct materials, direct labor, purchasing, and other overhead would remain the same, but the total cost would be less because the engineering cost would be omitted.