Assume you have a 3-step process using 3 machines with deterministic activity times of 15 min, 20 min, and 15 min respectively and it costs $10 to add a machine at any step. How much can you increase capacity if you invest $20 = ($10*2) to add machines?

Group of answer choices

From 4 units per hour to 6 units per hour.

From 4 units per hour to 8 units per hour.

From 3 units per hour to 6 units per hour.

From 3 units per hour to 4 units per hour.

None of the above.