Arnold goes to the gym and needs proteins to gain muscles. He can eat beef or drink protein shakes. Noting B the quantity of beef (in kg) and S the quantity of shakes (in liters), Arnold's utility is: U(B, S) = 2 S + log B. Arnold's weekly budget for his diet is 5. The cost of a kg of beef is 1. Eating beef has a high ecological footprint. The owner of the shakes shop is an environmental activist and does not want Arnold to eat too much beef. What is the maximum price of a liter of protein shakes such that Arnold eats less than 1kg of beef? (Hint: a lot of points will be granted for the reasoning. Using a solver for the final steps is highly recommended!)