I had this question in a test and had no idea how to answer it.

The function $\displaystyle C = 500(1-e^{-0.3x}) $ shows individual consumption spending (C) in $ as a function of income (x) in $000. At what income level will and individual have consumption spending of $400? You may find it helpful to use the fact that ln0.2 =-1.609 to 3dp.

Could someone please walk me through how i work these questions out , they really stump me.

Thanks.