A cabinet maker has 12 units of wood and intends to build two different kinds of bookcases in 36 hours. Model I requires 3 units of wood and 9 hours of labor, while model II requires 2 units of wood and 8 hours. The selling prices of the models are 150and90 respectively. How many bookcases of each model should the cabinet maker assemble in order to maximize his revenue? Construct a model to depict the situation and solve graphically to get an optimal solution

using graphic method