Using Solver in Constrained Optimization Model

Hi all,

I am trying to use solver to determine optimal assortment size by product to maximize sales while being below a space constraint.

See attached example.

However, when I try to use solver with the parameters:

Maximize Total Sales while constrained to Total Space Units < Max Space Units Possible while changing Product Sizes (B7:B9) it does not understand and makes the values in B7:B9 1.05 (which do not correspond to anything and return sales/space values of 0.

I want the solver to figure out while product size to reduce to fit the space requirement while maximizing sales. In this basic example, it would be by changing cell B9 to 4 and cell B8 to 3.

Is that possible to do with Solver? Might be too complex I'm not sure!