*Managed to confuse myself doing a probability assignment. Would like some confirmation on whether I've done it correctly*

You're selling three kinds of jewellery at a flea market. You have put up seven rings, four necklaces and nine bracelets for sale. Every item has the same chance to be sold.

In the first hour two sales are made

a. *(done this part, had to draw a chance tree)*

b. Calculate the probability that the two sold jewellery items are a ring and a bracelet *(this is just (16/20) or simplified (4/5) right? No particular order is mentioned but I'm not quite sure if I'm allowed to assume)*

c. Calculate the probability that the first two sales are not necklaces *(At first I assumed this would also be (16/20) but I wasn't quite sure so I looked at the chance tree i made in a. and it would be (8/12) or simplified (2/3). The assignment wants me to calculate it though so I'm again not sure)*

ORUL82 Sep 9, 2020