Data and Displays · Superchallenge problem

Data are grouped into the classes $0$–$10$ ($12$ values), $10$–$30$ ($18$ values) and $30$–$60$ ($15$ values). A student draws the histogram incorrectly, making each bar's height equal to its count instead of making each bar's area proportional to its count. The fraction of the drawn area taken by the $30$–$60$ bar is how many times the true fraction of the data in that class?