c. The question asks you to find the equation for the PEP. It allows you to set Py to 1.
This is really just a trick of algebra.
Which variables should be present in the PEP? What variable is it attempting to show? You should figure out which variables are on the axis for the PEP, and solve for the variable it is showing in terms of these.
Any equation in terms of the variables on the axis which demonstrates the right relationship will be sufficient.
d. Apply the same process, but ask which variables are on the axis of the IEP graph, and which variable is being allowed to vary.
These were the two hardest parts of the set and were designed to see who could solve them. I will weight them accordingly.
See you in class tomorrow.