Final answer:
The equipment elevator would be at a depth of 208 ft and the minors' elevator would be at a depth of 592 ft after 18 seconds. The minors' elevator is deeper at that time.
Step-by-step explanation:
To determine the position of each elevator after 18 seconds and which elevator is deeper at that time, we need to calculate the distance each elevator has descended.
The equipment elevator descends at a rate of 4 ft/s, so after 19 seconds, it would have descended 19 * 4 = 76 ft.
The minors' elevator descends at a rate of 16 ft/s, so after 19 seconds, it would have descended 19 * 16 = 304 ft.
After another 18 seconds, the equipment elevator would have descended a total of 76 + (18 * 4) = 208 ft.
Similarly, the minors' elevator would have descended a total of 304 + (18 * 16) = 592 ft.
Therefore, after 18 seconds, the equipment elevator would be at a depth of 208 ft relative to the surface, while the minors' elevator would be at a depth of 592 ft. Hence, the minors' elevator is deeper at that time.