Table:
text: Pace (transit)
Bus Fleet
Bus Fleet
Year_ Make_Model Length_ Engine_Type Numbers
2000-2004 Orion VI ft (m) Diesel 6000-6161 (160 buses)
2002 MCI D4000N ft (m) Diesel 6900-6907 (8 buses)
2003 NABI 40-LFW ft (m) Diesel 6162-6261 (99 buses)
2003 NABI 35-LFW ft (m) Diesel 6600-6684 (84 buses)
2005 NABI 40-LFW ft (m) Diesel 6262-6322 (60 buses)
2006-2010 ElDorado National EZ-Rider II ft (m) Diesel 2600-2825 (223 buses)
2012 ElDorado National EZ-Rider II BRT ft (m) Diesel 2826-2829 (4 buses)
2012 Orion VII 3rd Generation ft (m) Diesel-Electric 2830-2831 (2 buses)
2012-2013 ElDorado National Axess ft (m) Diesel 6323-6376 (54 buses)
2013 ElDorado National Axess Suburban ft (m) Diesel 6377-6391 (15 buses)

text: Pace (transit)
Bus Fleet
Bus Fleet
Year_ Make_Model Length_ Engine_Type Numbers
On Order On Order On Order On Order On Order
2014 ElDorado National Axess ft (m) CNG TBD (91 buses)
2014 MCI D4000CT and/or D4000CL ft (m) Diesel TBD (13 buses)

Question: If the length is ft (m) with numbers from 6600-6684 (84 buses) for 2003 what is the engine type for the pace?