Answer:
See below
Step-by-step explanation:
The computation of return on investment is seen below
= (Controllable margin ÷ Operating assets) × 100
= ($78,000 ÷ $300,000) × 100
= 26%
Now, the controllable margin equals to = $78,000 + $12,000
= $90,000
And the new operating assets would be;
= $300,000 + $90,000
= $390,000
So, the new return on investment equals to
= ($90,000 ÷ $390,000) × 100
= 23.08%
Therefore, the return on investment decreased by
= 26% - 23.08%
= 2.92%