Complete the cumulative frequency table for the data.

• At $x = 20$, the cumulative frequency is $y = 0$.
• At $x = 30$, the cumulative frequency is $y = 10$.
• At $x = 40$, the cumulative frequency is $y = 25$.
• At $x = 50$, the cumulative frequency is $y = 45$.
• At $x = 60$, the cumulative frequency is $y = 55$.
• At $x = 70$, the cumulative frequency is $y = 60$.

The "Percentage of Income" column will represent the upper class boundaries, and the "Cumulative Frequency" column will show the corresponding cumulative frequencies.

The completed cumulative frequency table is shown above.