A submarine moved from the water surface at a speed of (-20)m per minute.How far is the submarine from the water surface at the end of 7 minutes?

Hi,
A submarine move at the speed of -20m per minute that means it submerge 20m below sea in 1 min.
speed= -20m/min
time= 7 minutes.
distance= speed x time
distance = -20*7
              = -140m

distance submerged is -140 m.
so its 140 m below sea level. or 140m away from the water surface