Answer:
The rent should be $ 390 or $ 410.
Step-by-step explanation:
Given,
The original monthly rent of an apartment = $350,
Also, the original number of apartment that could be filled = 90,
Let the rent is increased by x times of $ 10,
That is, the new monthly rent of an apartment =( 350 + 10x ) dollars
Since, for each $10 per month increase there will be two vacancies with no possibility of filling them.
Thus, the new number of filled apartments = 90 - 2x,
Hence, the total revenue of the firm = ( 90 - 2x )(350 + 10x ) dollars,
According to the question,
( 90 - 2x )(350 + 10x ) = 31,980
By the quadratic formula,
Hence, the new rent of each apartment, if x = 6, is $ 410,
While, if x = 4, is $ 390
