Alice sent a total of 600 mails from Monday to Friday. How many mails

OFFICIAL EXPLANATION

In general, mail sending questions are hidden integer questions, so it is mostly 5051-level question, and also mostly related to CMT 3 (con 1) and con 2) are different questions), CMT 4 (A: if you get C too easily, consider A and B), and CMT 4 (B: if you get A or B too easily, consider D).

In the original condition, there are 5 variables (Mon ~ Fri) and 1 equation (600 mails sent in 5 days), and in order to match the number of variables to the number of equations, there must be 4 more equations. Therefore, E is most likely to be the answer. By solving con 1) and con 2) together, at least = minimum, so it means that from Monday to Friday, 120 mails were sent each day, which means 120 mails were sent on Monday as well, so it is unique and sufficient. Therefore, the answer is C. However, this question is an integer (hidden integer) question, one of the key questions, therefore you apply CMT 4 (A: if you get C too easily, consider A and B).

For con 1), even if 480 mails were sent from Mon to Fri, you are unable to find the number of mails sent on Mon, therefore it is not sufficient.
For con 2), at least 120 mails were sent every day from Mon to Fri, and in order to send a total of 600 mails for 5 days, at least 120 mails must be sent every day, which means 120 mails were sent on Monday as well. Hence, it is unique and sufficient. The answer is B.