The length of a rectangle is increasing at a constant rate of 3 cm/s, and its width is increasing at a constant rate of 0.5 cm/s. At the time the length is 5 cm and the width is 1.2 cm, how fast is the area of the rectangle increasing? (1 point)15.6 cm²/s6.1 cm²/s6 cm²/s1.5 cm²/s