Title:
<h2>The worker's highest wage is $400.</h2>Step-by-step explanation:
Due to the joining of the 11th worker, the firm's output increases 10 units.
The price of each unit is $40.
The price of 10 units are .
The worker's wage will be highest if he will be paid all the amount which is the resultant of the output's increase, that is (90 - 80) = 10 units.