Barbara is trying to better understand her company's overhead costs to respond to an e-mail from her supervisor. She quickly gathered information from the last 3 months regarding production counts and key overhead costs, as follows. (a) Based on just the information provided above, help Barbara classify each of the three costs by behavior: variable, fixed, or mixed. If these 3 months are representative of the company's typical production, what is its relevant range? The relevant range is from units to units