Answer
The unit cost of the heat pump will be lower.
Work Step by Step
Furnace: $C=\ 1.42/therm\times1\ therm/105,500\ kJ\div0.97=\ 13.9\times10^{-6}/kJ$
Heat Pump: $C=\ 0.11/kWh\times1\ kWh/3600\ kJ\div3.5=\ 9.13\times10^{-6}/kJ$
The unit cost of the heat pump will be lower.
