collection area of solar water heater? given energy of sunlight in kj and how much to install given price/m2?

The average home has a 200 liter (50-60 gallon) hot-water tank, which is effectively drained and replenished three times per day. Assume that the entering tap water is 19 degrees C and is heated to 51 degrees C. Given an average energy from sunlight of 1.53 kJ/cm2 per day, how large would the collection area (in m2) of a solar water heater need to be if its efficiency is 26%? Assume that the price of a solar collector is $375/m2. How much would it cost to install this hot water system?

I don't know where to begin on this.  Please give me the answers and formulas used.