Lets say that is first type of shares and is second type of shares.

So you can buy total shares:

In order to earn $540 you must set following equation:

So you have systems of equations:

We solve first equation for :

We susbtitute in second equation:

We susbtitute in first equation:

So solution is that you have to buy 100 shares of $32 and 300 shares of 23$.