Write an Equation That Expresses the Relationship

Multiple Choice

Write an equation that expresses the relationship. Use k as the constant of variation.
-The intensity I of light varies inversely as the square of the distance D from the source. If the intensity of illumination on a screen 36 ft from a light is 3.9 foot-candles, find the intensity on a screen 90 ft from the light.

A) 0.624 foot-candles
B) 1.56 foot-candles
C) 9.75 foot-candles
D) 24.38 foot-candles