#### Answer

a)$0.25$
b)$0.55$

#### Work Step by Step

We know that probability$=\frac{\text{number of favourable outcomes}}{\text{number of all outcomes}}.$
There are $8+5+4+3=20$ bottles in total.
a) $5$ are bottles of Coke, hence the probability: $\frac{5}{20}=0.25$
b) $8+3=11$ are bottles of Pepsi or IBC, hence the probability: $\frac{11}{20}=0.55$