15. (4 marks) Michael wanted to measure the softness of bread in his group project. Kevin proposed to do so by putting an object on top of the bread and letting it press the bread downwards. The softness can then be quantified by the time taken for the object to stop at a certain distance. The shorter it takes, the softer the bread is. Kevin suggested that the movement of the object on the bread can be modelled by the following differential equation, which is originally related to studying the motion of a mass attached to a spring: C+ 207 +64r = 0, where r (measured in cm) is the distance of the object at time (in seconds) below its starting position. In Kevin's suggestion, x(0) = 0 and the initial velocity of the object was 0.6 cm/s. This means r'(0) = 0.6. Where would the object be after 0.1 seconds (correct to 3 significant figures)? ->(-20.06) (A) This cannot be determined as I did not attend the group presentations. (B) )0.0234 cm (C) 0.0436 cm (D) 0.0645 cm (E) None of the other options. [Total of Section A: 20 marks]