Astronauts in space “weigh” themselves by oscillating on a spring. Suppose the position of an oscillating 75 kg astronaut is given by x = (0.30 m) sin((p rad/s) × t), where t is in s. What force does the spring exert on the astronaut at

(a) t = 1.0 s and

(b) 1.5 s? Note that the angle of the sine function is in radians.