How can I find optimal value for inputs regarding outputs value with specific feature in ANN?

I have 3 inputs(x1,x2,x3) and 4 outputs(y1,y2,y3,y4) with 60 datasets. I want to know if the y1 and y2 are minimum, y3 is maximum, and y4 is in the specific interval, how much could be the inputs optimum value.