Answer please

Hi! Please provide me the correct answer for this question..

A business owns some land that could be sold for $1 million and which cost $800,000 two years ago.
Alternatively, the land could have apartments build on it for a present cost of $5 million. The
apartments would bring in rent of $550,000 pa in perpetuity from time 1 onwards.
Discount rate = 10%
What is the NPV of the project?

Is my answer correct?

NPV of taking on the project of building the apartment instead of selling =
-5000000 (Present cost)
-1000000 (Opp cost of not selling the land now)
+5500000 (550000 x 1/0.10)
= -500000 therefore the project shouldn’t be taken on.
Obviously the 800000 cost two years ago is a sunk/past one & hence irrelevant.