a) The number of pages prints at t=0 is p0=0.
The number of pages prints at t=4 minutes is P1=64 pages.
The first coordinate of the graph is (a, b)=(0, 0).
The second coordinate of the graph is (c, d)=(10 min, 250 pages). The expression for the rate of the pages printed by the first printer is,
r1 = p1 - p0 / 4-0
Substitute the given values in the above expression.
r1 = 64 pages - 0 / 4 minutes - 0
= 16 pages / min
b) Printer 1 prints at an exponential rate. Both the x and y values increase by a constant ratio of 2. We can either use a logarithm of the first printer or find a constant number of documents it can print / time to become proportional.