Suppose that the local sales tax rate is $4 \%$ and you purchase a car for $\$ 20,700$.
a. How much tax is paid?
b. What is the car's total cost?
a. The amount of tax paid is $\$ \square$.
b. The total cost is $\$ \square$.

Step 1 ：Suppose that the local sales tax rate is 4% and you purchase a car for $20,700.

Step 2 ：To find out how much tax is paid, we need to multiply the cost of the car by the tax rate. In mathematical terms, this can be represented as \(20700 \times 0.04\).

Step 3 ：Calculating the above expression gives us the tax amount, which is $828.

Step 4 ：To find the total cost of the car, we need to add the tax amount to the original cost of the car. In mathematical terms, this can be represented as \(20700 + 828\).

Step 5 ：Calculating the above expression gives us the total cost, which is $21528.

Step 6 ：Final Answer: a. The amount of tax paid is \(\boxed{828}\). b. The total cost is \(\boxed{21528}\).