Using Solver in Excel, Flow in Flow out models. Please help

Problem: 1 - You are managing three separate construction sites, each requiring a minimum amount of gravel to be delivered one week. The individual site needs correspond 2,500 , 3,750 and 4,850 tons respectively for job sites 1,2 and 3. There are three different gravel pits in the area, all owned by the "Bob" family. Below is the table representing costs from each gravel pit and the available supply. Transportation Costs Per Ton a) A: Setup the problem and solve in Excel b) Interpret the results c) Which gravel pit is most important? Available Supply of Weekly Gravel d) Which job site is most difficult to supply? e) How would the solution change if both Ray-Bob and Jay-Bob could ship to BobBob for $1 per ton