Consider the common mirage associated with an inhomogeneous distribution of air situated above a warm roadway. Envision the bending of the rays as if it were instead a problem in total internal reflection. If an observer, at whose head $n_{a}=1.00029,$ sees an apparent wet spot at $\theta_{i} \geq 88.7^{\circ}$ down the road, find the index of the air immediately above the road.