If a vector A has components Ax < 0, and Ay < 0, then the angle that this vector makes with the positive x-axis must be in the range
cannot be determined without additional information
270° to 360°
90° to 180°
0° to 90°
180° to 270°

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?