Let F(x, Y, Z) Be the Amount of Heat Lost $\frac { \partial f } { \partial z }$

Multiple Choice

Let f(x, y, z) be the amount of heat lost each day by a rectangular building x feet wide, y feet long, and z feet high. Suppose that $\frac { \partial f } { \partial z }$ (50, 80, 15) = 45. Which one of the following conclusions can be drawn?

A) A building with dimensions 51 × 81 × 16 will lose about 45 more units of heat each day than a building with dimensions 50 × 80 × 15 .
B) A building with dimensions 50 × 80 × 15 loses about 45 units of heat each day.
C) A building with dimensions 50 × 80 × 16 will lose about 45 more units of heat each day than a building with dimensions 50 × 80 × 15 .
D) A building with dimensions 50 × 80 × 15 loses about 45 units of heat from the top of the building each day
E) The marginal heat loss per day is 45 units of heat per square foot of surface area of the roof.