Homework question about gears.

This question has stumped my TA!

The setup is this: I have a line or “train” of four interlocking gears (sort of like this, except there’s 4) of different sizes. The radius of each gear is known, the number of teeth on each gear is known, and the angular velocity of the “input” gear is known. The efficiency of each gear interaction is 93%. I am to find the torque available on the output gear.

We have learned some formulas for finding torques in gear trains, but they are all expressed as ratios, e.g. (torque in)/(torque out) = (number of teeth on input gear)/(number of teeth on output gear). So without knowing the torque on any of the other gears, I don’t know how to find the torque on the output gear. I’ve researched other relationships between torque and gear properties and haven’t found anything useful for the information I have.

Any jelly that can help gets my eternal gratitude.