(A) The cumulative frequency for the given data is calculated as follows:
| Class interval | Frequency | Cumulative frequency |
| $0-10$ | $5$ | $5$ |
| $10-20$ | $x$ | $5+x$ |
| $20-30$ | $20$ | $25+x$ |
| $30-40$ | $15$ | $40+x$ |
| $40-50$ | $y$ | $40+x+y$ |
| $50-60$ | $5$ | $45+x+y$ |
From the table,the total frequency $n = 60$.
Thus,$45+x+y = 60 \implies x+y = 15 \dots (1)$.
The median is $28.5$,which lies in the class interval $20-30$.
Therefore,the median class is $20-30$.
Lower limit $(l) = 20$,frequency $(f) = 20$,cumulative frequency $(cf) = 5+x$,and class size $(h) = 10$.
Using the median formula: $\text{Median} = l + \left( \frac{\frac{n}{2} - cf}{f} \right) \times h$.
$28.5 = 20 + \left( \frac{30 - (5+x)}{20} \right) \times 10$.
$8.5 = \frac{25-x}{2}$.
$17 = 25 - x \implies x = 8$.
Substituting $x=8$ into equation $(1)$: $8+y = 15 \implies y = 7$.
Thus,$x = 8$ and $y = 7$.