thermostat replacement

My friend wants me to install a programable thermostat for him. The unit is a Coleman heat pump model 3736-811 with a gas furnace. The t-stat is a Honeywell RTH 7500.
The connections on the old t-stat are W2-grey wire, G-green, R-red, L-white, X-black, O-orange, Y-yellow, B-blue.
The problem is that there is no C wire on the old t-stat.
Any help would be appreciated.
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