From sea level, a submarine descends 20 feet per minute. Where is the submarine in relation to sea level 5 minutes after it starts descending?
A. 20
B. 5
C. 100
D. -100
E. -20

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m