打算装新的HVAC，招了三家来估价，有一家是$4995：
We propose to furnish all labor, material and equipment to install Quality
Heating & Cooling Systems Using Carrier Cooling & Heating Equipment in
accordance with the following conditions and specifications:
Equipment: 15 SEER 12.5 EER 8.7 HSPF
1 Carrier 25HCC542A003/ 3.5-Ton Comfort 15 Series Puron Heat Pump
1 Carrier FX4DNF043T00 Comfort Series Speed Fan Coil
1 Carrier KFCEH3001F15 15-KW Electric Heater Package
1 Carrier TC-PHP Comfort Series Programmable Thermostat
另外一家$5600：
Rheem 3-1/2 Ton 15 Seer Heat Pump System. This system includes the air
handler, a 15 kw heater and the outdoor heat pump unit. This system will
host the environmentally friendly R-410A refrigerant. This system qualifies
for the Federal Tax Credit. AHRI#3592094 The actual Seer rating of this
system will be 15.5 Seer, 13Eer and 10 HSPF.
Model # of Heat Pump: RPQL036JEZ
Model # of Air Handler: RHLLHM4821JA
Model # of Strip Heater: RXBH24A15J
Model # of Filter Base: FFR24
Model # of Filter: FFR24-FILTER
网上搜了一下，发现前三项两家都一样。第二家多了filter和filter base，这是什么
？懂行的给介绍一下？谢谢！
