Tristan Wire Company heats copper ingots to very high temperatures by placing the ingots in a large heat coil. The heated ingots are then run through a shaping machine that shapes the soft ingot into wire. Due to the long heat-up time, the coil is never turned off. When an ingot is placed in the coil, the temperature is raised to an even higher level, and then the coil is allowed to drop to the "waiting" temperature between ingots. Management needs to know the variable cost of power involved in heating an ingot and the fixed cost of power during "waiting" periods. The following data on ingots processed and power costs are available: Using the high-low method, estimate a cost formula for power cost. (X represents per ingot.) Express the formula in the form Y = a + bX