I have to solve this:

Minimize C = 30x + 10y subject to

1.8x + 0.9 >= 270|

0.3x + 0.2y >= 54

0.01x + 0.03y >= 3.9

x, y >= 0

The corner points I got for the feasible area are (60, 180), (120, 90) and (102, 96).

The minimum value I got is C = 3600 when x=60 and y=180, but an online programming calculator I used to check my answer tells me that the correct answer is C = 3000 when x=0 and y=300. O_o. Help?