In a survey on the speed of cars (in km/h) along a highway, one of the class intervals is recorded as 45–__ km/h.
Given that the class size is 8 km/h, answer the following questions.
(i) Find the missing upper class limit.
(ii) Calculate the class mark of this interval.
(iii) If the frequency of this class is 12, write the ordered pair (class mark,frequency) for use in further statistical calculations.