The eRDPml has three processes - Dive Planning, (minimum) Surface Interval and Maximum Depth and you'll have to go in and out of Dive Planning and Surface Interval and record all the bottom times, minimum surface intervals and required safety stops to get the answer as it's not looking for the dive time but the time it takes to complete all aspects of these profiles.
Start with Dive Planning and enter the relevant information for Dive 1. After this, it will you a pressure group designation and whether a safety stop is required. Remember this, you'll need it in a moment.
Now exit and go to Surface Interval. Enter the pressure group designation from the previous dive and the details of Dive 2. This will give you a minimum time which you should also record to get the answer. It may give you a required safety stop alert. This can be disregarded at this stage as you're about to step back in Dive Planning to input the relevant information.
Now you're back to Dive Planning and the eRDPml will ask you if it's the first dive and the answer is; no'. I will then ask you if you have the pressure group designation after the last dives surface interval; this throws a lot of people, answer 'no' to this question too.
You'll then be able to input the pressure group designation for the previous dive, the minimum surface interval you discovered from the Surface Interval process and the details of Dive 2.
Repeat the steps listed above for Dive 3 and then take all the bottom times, surface intervals and required safety stops, add them together and you'll have your answer.
Be aware of the W, X, Y and Z rule with these kinds of questions too.