The cumulative frequency graph shows distribution of the waiting times before being served, in minutes, of 60 customers at restaurant A on a particular day.

1. Identify the two middle values and calculate the median.

The data is already in ascending order:

$10, 12, 14, 14, 15, 17, 17, 18, 22, 28$

There are $10$ values, so the median is the average of the 5th and 6th values.

$\text{Median} = \frac{15+17}{2}=16$

1. Find the lower quartile and upper quartile from the ordered data.

The data is already in ascending order:

$10, 12, 14, 14, 15, 17, 17, 18, 22, 28$

Lower half: $10, 12, 14, 14, 15$, so $Q_1=14$.

Upper half: $17, 17, 18, 22, 28$, so $Q_3=18$.

2. Calculate the interquartile range.

$\text{Interquartile range}=Q_3-Q_1=18-14=5$

1. Give a valid reason why the comparison is unfair.

Restaurant A's data is based on $60$ customers, while restaurant B's data is based on only $10$ customers. Since the sample sizes are very different, the data from restaurant B may not be representative enough to compare fairly with restaurant A.