Radar Observations Are Used from Venus-Orbiting Spacecraft to Evaluate Mountain $\mu$

Radar observations are used from Venus-orbiting spacecraft to evaluate mountain heights by measuring the time difference between echoes from mountain peaks and from the surrounding plains. In this technique, what would be the time difference for signals reflected from Maxwell Montes, which rises 12 km above the plain? (Think about the geometry and total path length.)

A) 80 ns, or 8 *10^-8 s
B) 800 ns, or 8 * 10^-7 s
C) 80 ms, or 8 *10^-2 s
D) 80 $\mu$ s, or 8 * 10^-5 s