Hypothesis Testing

A manufacturer of automatic washers offers a model in one of three colors: A, B, or C. Of the first 1000 washers sold, 400 were of color A. Would you conclude that customers have a preference of color A? Justify your answer.

I have no idea how to answer this, there is no significance level. I also don't know what the null and alternate hypothesis would be. Please Help!

Start by asking "How many of that color machine would you expect to have been sold?"
if there was no preference based on color.
You can say the null hypothesis is .... there is no preference
and the alternative hypothesis is.... there is a preference.

Usually when there is no significance, you assume .05