The cost C of manufacturing a product can be estimated by the formula C= 0.03 rs t^2, where r ans s are amounts, in pounds, of two major ingredients and t is production time in hours. if r is increased by 50%, s increased by 20% and t decreased by 30%, by approximately what % will the estimated cost of manufacturing the product change.	Choose one
A) 40% increase  B) 12% increase  C) 4% increase  D) 12% decrease  E) 24% decrease
Let r=s=t=100   C = 0.03*r*s(t^2)   =0.03*100*100*(100^2)   =3,000,000   r1 = 50% more than r = 150   s1 = 20% more than s =120   t1 = 30% less than t = 70   C1= 0.03 * 150 *120 * 70 * 70   =0.03 * 1800 * 4900   = 54*4900= 
<gadget id="calculator">54*4900</gadget>
<output>264_600</output>
264600   12% decreaseecrease= C-C1 = 3,000,000-264600=35400   %12% decreaseecrease = 35400/300000 * 100 = 354/30= 
<gadget id="calculator">354/30</gadget>
<output>59/5 = around 11.8</output>
11.8 ~ 12% 12% decreaseecrease   ANSWER:12% decrease
<result>D</result>
The cost C of manufacturing a product can be estimated by the formula C= 0.03 rs t^2, where r ans s are amounts, in pounds, of two major ingredients and t is production time in hours. if r is increased by 50%, s increased by 20% and t decreased by 30%, by approximately what % will the estimated cost of manufacturing the product change.