The can is 10 inches long, 8 inches wide, and 12 inches high.
As, Volume of cuboid =

Volume of can =
cubic inches.
So. Volume of can = 960 cubic inches.
Since, a gas can is filled at the rate of 320 cubic inches per minute.
Therefore, total minutes taken to fill the can = Volume of the can
Rate at which gas is filled
=

= 3 minutes.
Therefore, it will take 3 minutes to fill the can.