In a Physics lesson, Chantelle adds weights to a spring and carefully measures the extension. She finds that the weight, y g is related to the extension, x cm by the formula y = 0.5x + 1 for 0 ≤ x ≤ 20. a Draw the graph of y against x for 0 ≤ x ≤ 20. b Use this graph to find the (i) weight for a 17 cm extension (ii) extension produced by a 5 g weight. c What would Chantelle's formula predict for the springs extension for a 1 kg weight? Comment on your answer