b$.$ The company also produces two refrigerator models: large $(L)$ and medium $(M).$ Although materials to produce the refrigerators is

available, fabrication time and assembly time are limited$.$ There are $540$ hours available for fabrication and $600$ hours available for

assembly this week. Each unit of model L requires $6$ hours for fabrication and $3$ hours for assembly, and each unit of $M$ requires $4$

hours for fabrication and $5$ hours for assembly. Each unit of $L$ contributes $$50$ to profit, and each unit of model $M$ contributes $$40$ to

profit. How many units of each model should be produced if the objective is to maximize profit? $($Round $"$L$"$ to $2$ decimal places.$)$

Use either the objective function or enumeration method.