This is a gut check as well as about pacing. Using descending rep schemes is super helpful in these cases. Try something like 10-8-6 and it gets you to 24 reps. 2 times through that and you get the idea. The burpee is going to boil down to consistency and making sure that you keep moving. It’s easy to slow here but try to keep a strong pace. If you need to modify try keeping the same weight and adjusting the reps to 35 of each in order to meet the goal time domain.