The table below shows the distribution of the waiting times for some customers in a certain petrol station. Waiting time (in mins) No of customers 1.5 - 1.9...

The table below shows the distribution of the waiting times for some customers in a certain petrol station.

(a) Write down the class boundaries of the distribution.

(b) Construct a cumulative frequency curve for the data;

(c) Using your graph, estimate: (i) the interquartile range of the distribution ; (ii) the proportion of customers who could have waited for more than 3 minutes.