A furniture dealer purchased a desk for 150$ and then set the selling price equal to the purchase price plus a markup that was 40% of the selling price. If the dealer sold the desk at the selling price, what was the amount of the dealer's gross profit from the purchase and the sale of the desk?

a. 40$
b. 60$
c. 80$
d. 90$
e. 100$

OA is e

Can someone please explain how to get to this answer... must be the GMAT friday evening sickness I'm having.

thanks