A student writes the results of some calculations and roundings in her laboratory notebook. Each result should follow the NCERT rules for significant digits and for rounding off. (i) $2.5 \times 1.25$ is reported as $3.1$. (ii) $4.52\ \text{m} - 2.1\ \text{m}$ is reported as $2.42\ \text{m}$. (iii) $2.865$ rounded off to three significant digits is reported as $2.87$. (iv) $0.04060\ \text{g}$ is reported to have four significant digits. (v) A class register shows 40 students, and this number has an unlimited number of significant digits. How many of the statements above are correct?