Physicians Systems Consultants, Inc., is a company that provides clinical and business software and support services for medical offices. PSC's "Limited Support Plan" offers software support consultation services by phone under the following terms:

• $50 per month; plus
• $1 per minute of phone consultation service with a minimum charge of 40 minutes per month (i.e., minimum charge of $40 per month)

Given this price schedule, what is the incremental/marginal cost to a PSC customer of using the30thminute of support services in a given month under this plan?

$1.66

Zero

$1.00

$2.66

Can't say without knowing the customer's demand for support services.