17. The marginal rate of technical substitution equals A) the marginal rate of substitution in equilibrium. B) the ratio of the marginal products of the inputs. C) the ratio of the amount of capital employed to the amount of labor employed. D) the slope of a ray from the origin to an isoquant.

20. If isoquants are drawn as straight lines, it implies that A) the two inputs are perfect substitutes for each other. B) the MRTS is decreasing. C) that the inputs must be used in fixed proportions. D) none of the above.

22. If isoquants are drawn as right angles, it implies A) that the MRTS is constant. B) that the inputs must be used in fixed proportions. C) that the two inputs are perfect substitutes for each other. D) none of the above.

25. Assume that the Donnell corporation is currently producing 500 units of output per period, using 25 units of labor and 20 units of capital. Values for the marginal product of each input and the prices of the inputs are as follows: MPK = 100, MPL = 200, w = 2, and r = 3. Given the information above, which of the following are true? A) The firm is currently using the optimal levels of capital and labor. B) The firm is not currently using the optimal levels of capital and labor and should increase labor and reduce capital. C) The firm is not currently using the optimal levels of capital and labor and should increase capital and reduce labor. D) The firm is not currently using the optimal levels of capital and labor, but it is impossible to determine how capital and labor should be reallocated.

Please provide thorough explanations.