74. 30 students from five courses came up with 40 problems for the olympiad, with students from the same course coming up with the same number of problems, and students from different courses coming up with a different number of problems. How many students came up with exactly one problem?
74. Let's choose 5 students, one from each year. Each of them came up with a different number of problems. Therefore, the total number of problems proposed by them is no less than $1+2+3+4+5=15$. The remaining 25 students came up with no more than $40-15=25$ problems. It is clear that each of them came up with one problem, and thus, a total of 26 people came up with one problem each.