The Position of an Air-Track Cart That Is Oscillating on a Spring

Multiple Choice

The position of an air-track cart that is oscillating on a spring is given by the equation x = (12.4 cm) cos[(6.35 s^-1) t].At what value of t after t = 0.00 s is the cart first located at x = 8.47 cm?

A) 4.34 s
B) 0.108 s
C) 0.129 s
D) 7.39 s
E) 7.75 s