Longitude of an airplane crossing the equator

An airplane flew from Davao City whose latitude is 14° N and longitude of 121.5° E on a course of S 30° W and maintaining uniform altitude. At what longitude will the plane cross the equator?
A. 110° 30' East
B. 122° 26' East
C. 113° 33' East
D. 116° 11' East