Case purpose: to understand the application of cost-volume-profit analysis.

1. The director's opinion is incorrect.

2. The production section chief:

Variable cost: 4.025+0.975+3.125 * 20%+1* 20% = 5.825 yuan per pair, profit: 7.5-5.825= 1.675 yuan per pair, so we should accept the order. The reason why the fixed cost is not calculated is because it will happen whether the fixed production cost is added or not; Because the other party comes to the door himself, there is no need for sales expenses, so the sales expenses are not calculated.

3. Sales section chief:

Variable cost of normal sales: 5.825+0.5=6.325 yuan per pair, total: 6.325 * 80,000 yuan = 506,000 yuan.

Variable cost of additional orders under normal production capacity: 5.825 * 20,000 =116 500 yuan.

The variable cost of additional orders exceeding the normal production capacity: 5.825+ 1.8=7.625 yuan per pair, totaling 7.625 *10,000 = 76 250 yuan.

Fixed cost: (3.125+1) * 80% * 80000 = 264000 yuan.

Total cost: 506 000+116 500+76 250+264 000 = 962 750 yuan.

Income: 800,000+30,000 * 7.5 =1025,000 yuan.

Profit before tax: 1 025 000-962 750=62 250 yuan.

4. The scheme of the sales section chief should be adopted.

5. The pre-tax profit becomes: 62,250+1.8 *110,000-40,000 = 40 250 yuan, so the sales section chief scheme should still be adopted.