Median from a cumulative frequency curve, missing class frequencies and estimated mean of grouped times

The times, \(t\) minutes, taken by \(56\) cyclists to ride up a hill were recorded. The cumulative frequency curve below summarises these times.

1. Use the curve to estimate the median time.[2]
2. The same times are grouped in the table below, where \(p\) and \(q\) are positive integers.

   Time (\(t\) minutes)	Number of cyclists
   \(20\leq t<24\)	\(3\)
   \(24\leq t<28\)	\(p\)
   \(28\leq t<32\)	\(19\)
   \(32\leq t<36\)	\(q\)
   \(36\leq t<40\)	\(6\)

   1. Find \(p\) and \(q\).
   2. Using the table, estimate the mean time, correct to four significant figures.[5]