She picks two $13$s, one $14$, three $15$s, five $19$s, and four $20$s.  The mode is $19.$  The median is $19.$  Thus, their difference should be $0.$ 
Amy picks some number cards as shown below:  $13, 20, 14, 15, 19, 20, 20, 19, 19, 15, 19, 19, 20, 13, 15$.  What is the difference between their mode and median? 

a. $$0$$ 
b. $$1$$ 
c. $$2$$ 
d. $$19$$ 
e. $$20$$ 