[tex] P(B|A)=\dfrac{P(A \cap B)}{P(A)}\\\\
|\Omega|=20\cdot19=380\\
|A|=5\cdot19=95\\
|A\cap B|=5\cdot4=20\\\\
P(A)=\dfrac{95}{380}=\dfrac{1}{4}\\
P(A \cap B)=\dfrac{20}{380}=\dfrac{1}{19}\\\\
P(B|A)=\dfrac{\dfrac{1}{19}}{\dfrac{1}{4}}=\dfrac{1}{19}\cdot4=\dfrac{4}{19}\Rightarrow B [/tex]
