729=_^3 how do you find the base

Find the volume of the solid obtained by rotating the region enclosed by the curves y=1x and y=7^-x about the x-axis. (use symbolic notation and fractions where needed.) volume =

Me d is also an option but i couldn't get it in the picture

Tobias gold sells computers at the office center he's guaranteed a minimum salary of $1,959 per month plus 6.3% commission on total sales how much in total sales is he