Hello again,
We had to use CAR (rate-limit) in the previous section 7 to complete the objectives specified in the task. This could NOT have been achieved by MQC because of the fine granularity specified in the task - ie mark packet that conforms to average rate with a certain mpls-exp value and packet that over the average rate but within the specified burst rate, a different mpls-exp value. This would require the continue keyword (just like access lists) in CAR.
If we had attempted Sect. 7 using the MQC method, we would still have to classify the packets by an access-list, as we have done for rate-limit and then call up that class map under the policy-map. Once we are here, we can only perfom the SET (police) actions on the packets already matched by the class map (marked by source/destination access list).
BUT for MQC, if a packet has already been matched within a class-map sequence, we can only police it once and then move to next class map. However, as said earlier, the section 7 tasks require that we perform at least 2 different mark actions - setting different mpls-exp values - based on the input traffic rate). We can only achieve this by using the brilliant CAR tool. In fact the hint is already in the questions (...RATE)!
Having said all that (if you are still reading), I'll answer your questions. We could have used MQC for Task 8.1 (easily - if it was on a different router), but once we configure input CAR on an interface (R6) - we cannot configure an input service-policy any more. So we have to continue using CAR (you can configure multiple CAR statements on an interface). Hope that answers your first question!
For your second question - CIR values. The CIR is in BITS/s and the Burst is in BYTES (BITS/8) per Time interval -Tc.
So here the question says CIR is 500kB/s (500,000B/s)
Normal Burst (amount of bytes to burst in Tc) = (Byte Value of the CIR)/Tc
Now am not sure I agree with the Tc value used to arrive at the IE solution but am not really worried about that. The formula above is how you arrive at the answer.
The Tc would be another one for the Proctor in the lab.
Cheers