As can be seen from the figure 1, the relationship between sales unit price and month is a linear function, while the relationship between cost and sales month is a quadratic function.

So let the sales month be X, the sales unit price be y 1, the sales cost be y2, and the profit be Y.

Therefore, the function in figure 1 is y 1=(-2/3)x+7.

The function formula in Figure 2 is: y2 = (1/3) * (x-6) 2+1.

Therefore, the monthly profit function is y = y1-y2 =-(1/3) * (x-5) 2+(7/3).

The vertex of this function is (5,7/3), so the profit from selling this dish in May is the largest.