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D( s )
100-(0.075*s) = 0
100-(0.075*s) = 0
100-(0.075*s) = 0
100-0.075*s = 0
100-0.075*s = 0 // - 100
-0.075*s = -100 // : -0.075
s = -100/(-0.075)
s = 1333.33333333
s in (-oo:1333.33333333) U (1333.33333333:+oo)
100-((7.84*s)/(100-(0.075*s))) = 0
100-7.84*s*(100-0.075*s)^-1 = 0
(-7.84*s)/(100-0.075*s)+100 = 0
(-7.84*s)/(100-0.075*s)+(100*(100-0.075*s))/(100-0.075*s) = 0
100*(100-0.075*s)-7.84*s = 0
10000-15.34*s = 0
(10000-15.34*s)/(100-0.075*s) = 0
(10000-15.34*s)/(100-0.075*s) = 0 // * 100-0.075*s
10000-15.34*s = 0
10000-15.34*s = 0 // - 10000
-15.34*s = -10000 // : -15.34
s = -10000/(-15.34)
s = 651.8904824
s = 651.8904824
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