Production/Storage Linear Programming Question - Solver Excel

Hi,

I've cracked my head over this question but still can't get it, help would be GREATLY appreciated!

Question

B Company is involved in the wheat business. B buys and sells wheat in bulk. B uses a warehouse for storage which charges $10/average ton of wheat stored per month (based on average of beginning and ending inventory each month). The warehouse capacity is 400tons at the end of each month. B estimates what he believes the price per ton of wheat will be during each of the next 6 months as summarized below.

Month 1 - $135

Month 2 - $110

Month 3 - $150

Month 4 - $175

Month 5 - $130

Month 6 - $145

Assume that B currently has 70 tones of wheat stored in the warehouse. How many tons of wheat should B buy and sell during each of the next 6 months to maximize his profit trading wheat.

**Formulate an LP model that would maximize B's profit**

Thank you!

Btw, any tips on how to better understand linear programming? I'm so lost at the formulation...