The distribution of income in a certain city can be described by the mathematical model $y=\left(5.6 \cdot 10^{11}\right)(x)^{-1.5},$ where $y$ is the number of families with an income of $x$ or more dollars.
a. How many families in this city have an income of $\$ 30,000$ or more?
b. How many families have an income of $\$ 60,000$ or more?
c. How many families have an income of $\$ 150,000$ or more