Probability

Can anyone help me with this question please?

In an experiment, 6 bulbs were planted in a row. 3 produced red flowers and 3 produced yellow flowers. If the bulbs were planted in a random order, what is the probability that the colours will alternate along the whole row?
The answer options are:-
1/60
1/48
1/32
1/20
1/10

There are \(\displaystyle \frac{6!}{3!3!}=20\) ways to arrange the bulbs.

But, out of this 20 ways, there is only two ways the whole row can have alternating colors:

RYRYRY

YRYRYR

So, what is the probability they alternate?.