Which of the following is an exogenous variable in the Three-Sector-Model?

Comment on the following statement: "In the short run, a firm's total costs will be zero if the firm chooses to produce nothing."

What will be an ideal response?

With an MPS of 0.3, the MPC will be:

A.  1 - 0.3 B.  0.3 - 1 C.  1/0.3 D.  0.3