Friction + Tension

[Sonryu]

Three blocks are connected by massless cords and rest on a frictionless horizontal surface. The blocks are pulled to the right. Mass m_1 = 2 m_2 = 3 m_3, with m_1 on the left and m_3 on the right. if the pulling force is equal to 90N, then the tension in the cord between m_1 and m_2 is...

 

a) 49

b) 15

c) 100

d) 44

e) 85

 

I realize that because the back block (m_1) is being pulled, only it's mass is used in calculating the tension. But beyond that, I'm lost. :/

[imatfaal]

No mass for m_3