$$5 \times 2 = 10$$ 
In a toy store, cars are available in $5$ different colours: blue, white, yellow, black and red. A car has either $2$ or $4$ doors. How many different version of the car are available? 
a: $$10$$ 
b: $$20$$ 
c: $$8$$ 
d: $$9$$ 
e: None of the above 