Please answer the solve the problems

1. A driver drives from A to B at 100 km/h and returns from B to A at 120 km/h. What is the average speed?

2. A fish stall in a vegetable market sells large crucian carp weighing 0.4 kilograms each for $20 per kilogram and small crucian carp weighing 0.25 kilograms each for $12 per kilogram. A customer asked the stall owner to buy one big and one small carp and weigh them together for $16 per kilogram. The stall owner agrees and asks who has the advantage in this sale? Why?

3. The grouped data of capital profitability and the data of annual profit amount of each group for 27 enterprises under a company are shown in the following table:

Grouped by capital margin%	Number of companies	Annual profit amount (million yuan)
Below 8 812 1216 1620 More than 20	2 6 12 5 2	300 1000 2600 1200 400
Total	27	5500

Please calculate:

(1) the average amount of profit per firm;

(2) The average capital profit margin for the entire firm (using absolute and relative weights, respectively).

4. The production of products in three workshops of an enterprise in a certain year is shown in the following table:

Workshop	Passing Rate%	Qualified products production (units)	Number of annual production hours (hours)
A B C	98 95 99	19600 18620 18434	6800 7200 8000
Total		56654	22000

Ask:

(1) If the 3 workshops complete the processing and assembly of a process of the whole product in turn, what are the total pass rate, average pass rate and average reject rate of the whole plant?

(2) If each of the three workshops completes the production and processing of the whole product, what are the total pass rate, average pass rate and average reject rate of the whole plant?

(3) If the three workshops produce different products (with different use values), what are the total qualification rate, the average qualification rate and the average scrap rate of the whole plant?