13. Draw the budget line for the following situations: a) You have an income of $40 per week to spend on two commodities. Commodity X costs $10 per unit and commodity Y costs $5 per unit; b) You have an income of $50 per week to spend on two commodities. Commodity X costs $10 per unit and commodity Y costs $5 per unit; c) You have an income of $50 per week to spend on two commodities. Commodity X costs $20 per unit and commodity Y costs $5 per unit; d) You got a $20 gift certificate, which can only be used to purchase commodity X. Your income is $50 per week, commodity X costs $10 per unit, and commodity Y costs $5 per unit