Just to be honest with you... I would never actually do this problem. However, I do have an asset called the internet that can help me. I believe that you have this asset too, because you are asking a question here. Now, there is this thing called a link that is a feature of the internet and if you CLICK the link, it takes you to something called a website. WOW! So, the link is:
Anyways, when clicking that link and plugging the numbers in, it gave me a result, a very big one. So I did something else, and clicked ctrl f and then searched "y4" without quotation marks. Then, it told me the coefficient was:
(If this answer is wrong, sue MathPapa not me)
That's the step-by-step process!