In a college library, four different business newspapers — Economic Times,…

In a college library, four different business newspapers — Economic Times, Business Standard, Business Line, and Financial Express — are available. All students visit the library regularly, but 20% of them do not read any business newspaper. The four newspapers, in the order given above, are read by 230, 180, 180, and 220 students respectively. For any two of the four newspapers, exactly 20 students read exactly those two newspapers. 30 students read all four newspapers, and no student reads exactly three of the four newspapers.

Suppose every student in the college — including those who currently read no newspaper — starts reading one additional newspaper (from the four listed above) that they are not reading at present; a student who already reads all four newspapers has none left to add and is therefore unaffected. What is the least number of students who then read all four newspapers?