JEE Advanced 2018 · Paper 1, Mathematics question 17

There are five students $S_1, S_2, S_3, S_4$ and $S_5$ in a music class and for them there are five seats $R_1, R_2, R_3, R_4$ and $R_5$ arranged in a row, where initially the seat $R_i$ is allotted to the student $S_i$, $i = 1, 2, 3, 4, 5$. But, on the examination day, the five students are randomly allotted the five seats.