Final answer:
A law enforcing a price ceiling on credit card interest rates below market equilibrium leads to an increased demand and decreased supply of credit, causing a shortage and leaving consumers without access despite their willingness to pay.
Step-by-step explanation:
The credit card market analysis demonstrates how the imposition of a price ceiling on interest rates can lead to a credit shortage. By setting the interest rate (Rc) below the market equilibrium rate (Ro), the law intends to make borrowing costs lower for consumers. However, the resultant credit shortage occurs because the quantity demanded for credit increases (moving from Qo to Qd), while the quantity supplied by credit card companies decreases (from Qo to Qs), leading to an excess of demand over supply. This scenario leaves many willing to pay the prevailing interest rate without access to credit cards because issuers are not willing to lend at the imposed lower rate.