Physcis question

In the given diagram, the coeff of static and kinetic friction are the same (0.25) between the two surfaces.  How much force is needed to push the 12kg block at a constant velocity to the left? (assume a perfect pulley system, and g = 10 m/s2; the top block stays on the bottom one).

Oh, here is the given diagram: http://img523.imageshack.us/img523/9982/physicscl1.jpg

oh ai no. it's 70, 50, 30, or 0. just take a guess or sth.

80, 50 etc but w/e.

Let's see... (8 Kg + 12 Kg) / (+0.25 - 0.25) = 20 / 0 OH SHI-