Question 388492
The feasible region is defined by plotting the bounding equations. 
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{{{drawing(300,300,-2,5,-2,5,grid(1),blue(line(1,100,1,-100)),circle(1,0,0.2),circle(4,0,0.2),circle(1,3,0.2),graph(300,300,-2,5,-2,5,0,4-x)))}}}
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The vertices are the points were the function maximum or minimum occur.
Check the value at each point.
({{{1}}},{{{3}}}):{{{f=2y+x=2(3)+1=6+1=7}}}
({{{1}}},{{{0}}}):{{{f=2y+x=2(0)+1=1}}}
({{{4}}},{{{0}}}):{{{f=2y+x=2(0)+4=4}}}

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C is the correct answer.