Answer
b. 15
Work Step by Step
Price of hot dog = \$2
Price of hamburger = \$4
Contribution of 30 hot dogs to GDP = \$2 * 30 = \$60
If the contribution of 30 hot dogs must be equal to that of hamburgers,
then number of hamburgers = \$60 $\div$ (Price of hamburger) = \$60 $\div$ \$4 = 15