* * * Need 1000×4=4000 yuan;
(2) Rent 3 carts, 156-42×3=30 people,
Rent a car: 30÷24= 1 (car) ... 6 people,
* * * Need1000× 3+600× 2 = 4,200 yuan;
(3) Rent 2 trolleys:
We also need to rent three cars: (156-42×2)÷24=3 (cars),
* * * Need1000× 2+600× 3 = 3,800 yuan;
(4) Rent 1 shopping cart:
Then we have to rent five cars: (156-42)÷24=4 (cars) ... 18 people,
* * * Need1000+600× 5 = 4,000 yuan;
Answer: From the above calculation, we can rent two buses and three cars to save money.