Juan and Pilar have a cycle race. The course consists of a flat stretch followed by an uphill, then a downhill and finally another flat road. Juan goes faster than Pilar on the flat but Pilar goes uphill quicker than Juan. Downhill they go at approximately the same speed as each other. The result of the race is that they cross the finishing line at exactly the same time. Which one of the following graphs best represents Juan’s lead over Pilar from the start of the race to the finish?