Solution: (1)∫ Unqualified: 50 ≤ x < 60, accounting for 10% in the pie chart.

Class size: 5 10%=50,

∴50×50%=25,

∴ 60 ≤ x < 70: 25-15 =10 (person)

∴ Good proportion:1-10%-16%-50% = 24%.

∴ number of people: 24%×50= 12 (person), as shown in the figure: ∴ grouping frequency 50 ≤ x < 60 560 ≤ x < 70? 1070≤x