please explain

1) You are watching an old adventure movie set in the Second World War (WW II) where a submarine is being kept in port by a destroyer cruising outside the port. The submarine slips out at dawn one morning and heads out to sea to intercept a convoy. The submarine travels during fourteen hours of daylight submerged at 10 knots and by night on the surface at 18 knots. The submarine will intercept at dawn two days after leaving port. Meanwhile word of the submarine's plans gets to the destroyer 24 hours after the submarine has left. The destroyer leaves immediately and manages to intercept the convoy just before the sub arrives. You know that the maximum speed of a WW II destroyer is 35 knots. Calculate how fast the destroyer had to travel to arrive at the convoy to see if the scenario plausible? One knot is 1 nautical mile per hour and one nautical mile is 1,852 m. 2) Order of magnitude estimate. A thunderstorm drops half an inch of rain on an area of 10 square miles. Estimate how many raindrops fell in the storm. Take the diameter of a raindrop to be 4mm. One inch is 25.4 mm and a mile is 1,609 m. 4 The volume of a sphere is: 3