After consuming what quantity of donuts does the consumer in the table below experience diminishing marginal utility?

What will an indifference curve look like between two commodities that are perfect complements, such as right shoes and left shoes?

What will be an ideal response?

In a command system, the decision about what should be produced is made by

a. a central authority b. the market c. repeating what was done in the past d. business firms e. consumers