Grabber - statics example

Hello,

We should get the length x , when the grabber can just hold the box.

grabber

I made two moment equations:
M1

M2

Then I put them together into one equation: m1m2

And from that equation I found out x: x

Unfortunately the result seems to be wrong. Can you please help me? Where I made the mistake?

72091_priklad.png

ΣMH=0

(xsinα)(12G)+12G(12b)=G2μ0(l1+l2)

x=2(l1+l2)μ0b2μ0sinα