Need help with calculus

3 (5) One ship is approaching a port from the east, traveling west at 15 miles per hour, and is presently 3 miles east of the port. A second ship has already left the port, traveling to the north at 10 miles per hour, and is presently 4 miles north of the port. At this instant, what is the rate of Change of the distance between two ships? Are they getting closer or further apart