4. -11 points SCalcET8 4.7.009.MI My Notes Ask Your Teacher A model used for the yield Y of an agricultural crop as a function of the nitrogen level N in the soil (measured in appropriate units) is kN 25 +N2 where k is a positive constant. What nitrogen level gives the best yield? Watch It Talk to a Tutor 5. -1 points SCalcET8 4.7.010. My Notes Ask Your Teacher The rate (in mg carbon/m3/h) at which photosynthesis takes place for a species of phytoplankton is modeled by the function where I is the light intensity (measured in thousands of foot-candles). For what light intensity is P a maximum? thousand foot-candles Need Help?Read It Talk to a Tutor 6. -12 points SCalcET8 4.7.014 My Notes Ask Your Teacher A box with a square base and open top must have a volume of 13,500 cm3. Find the dimensions of the box that minimize the amount of material used sides of base height Cm Cm Need Help? Talk to a Tutor