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A professor needs help from three student helpers to complete four tasks. Each student can only perform a single task. The first task is grading; the second is scanning; the third is copying, and the fourth is organizing student portfolios. The estimated time for each student to do each task is given in the matrix below. Task 1 Task 2 Task 3 Task 4 Student A 90 50 40 20 Student B 120 60 30 50 Student C 110 60 50 70 The professor wants to assign tasks such that the time is minimized and as many tasks get done as possible (but remember, one task per student). Which of the following represents the constraint for the assignment for student A? XA1 + XA2 + XA3 + XA4 > 1 XA1 + XA2 + XA3 + XA4 = 1 O XA1 + XA2 + XA3 + XA4 = 0 O XA1 + XA2 + XA3 + XA4