Write a piecewise function for the graph

What is the logarithmic function modeled by the following table? x f(x) 9 2 27 3 81 4

The u-drive rent-a-truck company plans to spend $13 million on 320 new vehicles. each commercial van will cost $25 comma 000, each small truck $50 comma 000, and each large truck  $80 comma 000. past experience shows that they need twice as many vans as small trucks. how many of each type of vehicle can they buy?

Solve for n? [tex]z = \frac{3}{4} mn[/tex]