Calculating Probability for Selecting Tanks with Specific Characteristics

[kschong]

For this question, i already solve the part a and part b. For the part c, i try to solve it but i can't get the answer that given. Can someone explain to me? How to do the part c. Thanks!

 

[tiny-tim]

Hi kschong!

So there's 24 tanks, of which 6 are high viscosity, add 4 are high impurity: what is the probability that 4 tanks chosen at random include exactly one of each?

Show us your full calculations, and then we can see what went wrong, and we'll know how to help.