Multiple Use Highrise Baseline Building(s)

Hello, We have a situation where we are attempting to model a highrise building of approximately 450,000 square feet. The predominant use of this building is residential. The proposed system will be a water source heat pump system. The residential portion of the building will be about 350,000 square feet. Therefore, we would foresee this being the predominant condition of this building. The other 100,000 square feet will be split between office and retail. However, at the time the model is to be submitted, the office and retail will only be core and shell and the fitouts will be done in the future. The proposed system in the office and retail spaces would be a water source heat pump system as well. I understand from CIR ID #10132 that the water source heat pump system is a ‘fossil fuel’ and we will choose the baseline systems accordingly. The questions are as follows: 1. G3.1.1a states to use additional systems and fuel sources for nonpredominant conditions over 20,000 square feet. Does this mean that the single proposed building would need to be compared with a baseline building for the residence AND a baseline building for the retail/office? Is G3.1.1a an option or a requirement? Can we model the proposed building against a single baseline building that is PTAC with Fossil Fuel Boiler if we would wish to? 2. If the core commercial spaces are not defined prior to the model as ‘retail’ or ‘office’, do we select one schedule and loading per ASHRAE and make them identical conditions in the proposed and baseline? 3. If we must differentiate ‘office’ and ‘retail’ and each type is over 20,000 square feet, does that push us into 3 different baseline buildings? One for residential, one for retail and one for office? Thanks in advance for any assistance you may be able to offer.