To determine how much you would pay for using a computer for 4 hours at the rates provided, we can break the problem into two parts:

1. Cost for the first two hours:
   The shop charges $P20.00$ per hour for the first two hours.
   Therefore, for 2 hours, the cost is: $2 \times 20 = P40.00$

2. Cost for the remaining two hours:
   After the first two hours, the shop charges $P10.00$ per hour for each additional hour.
   Therefore, for the remaining 2 hours, the cost is: $2 \times 10 = P20.00$

3. Total Cost:
   Adding the costs from the first two hours and the remaining two hours: $P40.00 + P20.00 = P60.00$

Thus, you would pay P60.00 for using the computer for 4 hours.

---

Would you like further details on the calculation or have any other questions?

Here are some related questions:

1. How would the cost change if you used the computer for 3 hours?
2. What if you used the computer for 5 hours instead?
3. How much would it cost for just 1 hour of use?
4. Can you calculate the cost for 6.5 hours of usage?
5. How would the total cost formula change if the rate for each additional hour was different?

Tip: When dealing with piecewise charges like this, always break down the time spent into the intervals where different rates apply.