【单选题】Samara's income is $30 a month and she spends all of it on music downloads and gasoline. The price of a music download is $3 and the price of a gallon of gasoline is $3. At Samara's best affordable po...
A.
0.5
B.
1
C.
1.5
D.
More information is needed to determine the marginal rate of substitution.