When interest rate increases, opportunity cost of holding money?

According to the Pew Charitable Trust methodology for identifying the middle class, for the period from 1971 to 2015, the middle class

A. decreased from 80% to 50% of the population. B. increased from 50% to 80% of the population. C. decreased from 80% to 71% of the population. D. increased from 71% to 80% of the population.

Figure 4.3 illustrates the demand for tacos. A successful advertising campaign to sell tacos would bring about a movement from:

A. point a to point b. B. point c to point b. C. D2 to D1. D. D0 to D1.