Final answer:
The profit earned for each hot dog sold is $2, as indicated by the constant of proportionality in the equation P = 2h.
Step-by-step explanation:
The equation P = 2h represents the proportional relationship between the profit earned (P) and the number of hot dogs sold (h). Here, the constant of proportionality is 2, which means that for every hot dog sold, the vendor earns $2 in profit. This constant is essentially the rate at which profit increases per hot dog sold and indicates that the profit is directly proportional to the number of hot dogs sold.