A developer is building a 60-unit apartment building. Construction will take 15 months covering all of Year 0 and the first 3 months of Year 1. Tenants will begin moving in the first day of Month 4. Lease up is expected to occur at a rate of 10 units per month until reaching full (100%) occupancy (e.g., 10 units occupied in Month 4, 20 units occupied in Month 5, etc.) What forecasted vacancy rate (average vacancy for the year) should be used for Year 1 in the pro forma? Assume 100% occupancy once fully leased up. (CAUTION: The question asks for the VACANCY percent, NOT occupancy percent.) (%)