A retailer bought a machine at a wholesale price of $90 and later on sold it after a 10% discount on the retail price.

[Gmat_mission]

A retailer bought a machine at a wholesale price of $90 and later on sold it after a 10% discount on the retail price. If the retailer made a profit equivalent to 20% of the whole price, what is the retail price of the machine?

(A) 81
(B) 100
(C) 120
(D) 135
(E) 160

Answer: C

Source: GMAT Prep