A mixture of two commodities A and B is in the ratio x:y. Commodity A costs Sh. 60 per unit and commodity B costs Sh. 72 per unit. If the mixture is sold at Sh. 78 per unit, what is the profit percent

Let the ratio of commodity A to commodity B be $x:y$.
The cost of commodity A is Sh. 60 per unit.
The cost of commodity B is Sh. 72 per unit.
The total cost of the mixture is $C_{mix} = 60x + 72y$.
The total number of units in the mixture is $x+y$.
The average cost price per unit of the mixture is $\frac{60x + 72y}{x+y}$.

The selling price of the mixture is Sh. 78 per unit