I
Come up with 31421.8 KG
m/M=d/D
515-120= 395 = d
515+150= 665= D
m = not known
M = 52900
so now> m/ 52900 = 395/665
m/52900 = .5939849 = m = .5939* 52900= 31421.8
I usually draw a line for such questions and insert the valid info into it as so>
-150 0 120 515
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you know the weight and you know how far and what is the maximum it can move between -150 and 515.
Not sure if it's correct since I'm a bit tired right now.