Seeing how the total arm length is 25" then just multiply by 4 = 100 (100%).

So, multiply 15" arm x 4 = 60 (60% advantage of the lever) {so it should only "see" 40% of the weight}

and remaining arm of 10" = 10 x 4 = 40 (only a 40% advantage of the lever) {so it should "see" 60% of the weight}

Anyway, That how my brain sees it.