Blood types All human blood can be typed as one of $\mathrm{O}, \mathrm{A}, \mathrm{B},$ or $\mathrm{AB},$ but the distribution of the types varies a bit with race. Here is the distribution of the blood type of a randomly chosen black American:
$$\begin{array}{lcccc}\hline \text { Blood type: } & 0 & \mathrm{~A} & \mathrm{~B} & \mathrm{AB} \\\text { Probability: } & 0.49 & 0.27 & 0.20 & ? \\\hline\end{array}$$
(a) What is the probability of type $A B$ blood? Why?
(b) What is the probability that the person chosen does not have type $A B$ blood?
(c) Maria has type $\mathrm{B}$ blood. She can safely receive blood transfusions from people with blood types $\mathrm{O}$ and $\mathrm{B}$. What is the probability that a randomly chosen black American can donate blood to Maria?