Suppose the Temperature at Any Point $( x , y ) \text { in a steel plate is }$

Multiple Choice

Suppose the temperature at any point $( x , y ) \text { in a steel plate is }$ $T = 500 - 0.6 x ^ { 2 } - 1.5 y ^ { 2 }$ where $x$ and $y$ are measured in meters. At the point $( 8,7 )$ find the rate of change of the temperature with respect to the distance moved along the plate in the direction of the $x$ -axis. Round your answer to one decimal place.

A) $- 7.2 ^ { \circ } / \mathrm { m }$
B) $- 9.6 ^ { \circ } / \mathrm { m }$
C) $38.4 ^ { \circ } / \mathrm { m }$
D) $3.4 ^ { \circ } / \mathrm { m }$
E) $- 5.2 ^ { \circ } / \mathrm { m }$