The distance from the Sun can be approximated by the equation D = 2.5 cos[ 0.0172(n – 185)] +150, where D represents the distance in millions of kilometres and n represents the number of days into the year.

       i.  How far will Earth be from the Sun on March 21, the eightieth day of the year?

       ii.  Determine the range of distances that Earth can be from the Sun.

       iii.  What is the period of this cycle? Explain what the period means in the context of this question.