The Math of "The Martian" Sol 25

The base has a multivitamin supply that will last Mark almost 10 years, so he has enough vitamins and minerals. Careful rationing of the protein in the rations on hand will provide him with enough protein to last 4 years. So all he really needs is raw calories.

The ration packs that NASA sent with the mission were calibrated to have the proper calories per SOL. However since Mark plans to grow potatoes to supplement these ration packs, he needs to convert everything back to earth days because that’s what all his nutrition information is based on.
Ares 4, the next manned mission to Mars will land 1387 Sols from now (Sol 25), assuming it isn’t canceled due to Mark’s “death”. How many Earth days from now until Ares 4 lands?

If he eats 1500 calories per earth day his ration packs will last until SOL 392.2. How many calories does he currently have in the ration packs?

He believes that by employing aggressive farming tactics that aren’t normally necessary on earth he can grow 6.75 calories per square meter of soil per day.

He currently has 62 square meters of the Hab covered in soil. If he only uses this area to grow food, when will he run out?

The Hab has 92 square meters of floor space total. If he covers all of it with soil how long will his food last?

The two rovers also have emergency shelters that he can use, each has 10 square meters. He can also use five of the six beds to grow food, and two of the three lab tables. The bunks and lab tables are 2 square meters each.

If he uses all of those, how many square meters of farmland will he have. How long will the food last now?

How much water will he need now, for both him and the soil? How much is he short by?