Data and Displays · Hard problem

A cumulative frequency table for $70$ test scores reads: below $50$: $6$; below $60$: $15$; below $70$: $33$; below $80$: $52$; below $90$: $64$; below $100$: $70$. What percent of the students scored at least $60$ but below $80$? Round to the nearest tenth of a percent.