A student attempts to write the third derivative of y with respect to x as follows:
Step 1: y′=dxdy
Step 2: y′′=dx2d2y
Step 3: y′′′=dx2d3y
Which statement correctly evaluates the notation used in Step 3?
a) Step 3 is correct because a third derivative has a power of 3 only in the numerator.
b) Step 3 is incorrect because the power on dx should also be 3.
c) Step 3 is incorrect because it should be written as d3xd3y.
d) Step 3 is incorrect because it should be written as dx3dy3.