Caleb went into a cave. The light intensity (in candela per square meter, or \text{cd/sq. m}cd/sq. mstart text, c, d, slash, s, q, point, space, m, end text) as a function of depth inside the cave (in \text{m}mstart text, m, end text) is graphed. What is the approximate average rate at which the light intensity decreases, as Caleb goes from a depth of 5\text{ m}5 m5, start text, space, m, end text to a depth of 14\text{ m}14 m14, start text, space, m, end text?