Answer:
The savings from the switch is negative savings of $6300,in other words loss is recorded not savings in costs.
The interest would have to fall to 10% for the planned switch to production to be feasible.
Step-by-step explanation:
The extra cost savings of switching over to level production is given below
Cost savings $42000
interest on inventory finance($420000*11.5%) ($48300)
Negative savings ($6,300)
The company would a loss of $6300 if it switches to level production,hence it is advisable to shelve the plan for now.
However,interest rates would have to fall to 10% as calculated below to make the planned switch to level production feasible
new interest rate=savings/increase in inventory
=42000/420000*100
=10%