A Professor Needs Help from Three Student Helpers to Complete

Multiple Choice

A professor needs help from three student helpers to complete four tasks. 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.
$$\begin{array} { r r r r r } & \mathbf { 1 } & \mathbf { 2 } & \mathbf { 3 } & \mathbf { 4 } \\\hline \text { Student A } & 90 & 50 & 40 & 20 \\\mathbf { B } & 120 & 60 & 30 & 50 \\\mathbf { C } & 110 & 60 & 50 & 70 \\\hline\end{array}$$
-Which of the following constraints represents the assignment for student A?

A) XA1 +XA2 + XA3 + XA4 = 0
B) XA1 +XA2 + XA3 + XA4 = 1
C) XA1 +XA2 + XA3 + XA4 ? 1
D) XA1 +XA2 + XA3 + XA4 ? 0