The time spent on homework by 80 students is recorded in the table below:
Class interval (minutes): 0–10, 10–20, 20–30, 30–40, 40–60
Frequency (students): 4, 12, 24, 28, 12
When the median time is estimated from the corresponding histogram, it will lie in which class interval?
a) 10–20
b) 30–40
c) 20–30
d) 40–60