Checking the ring k[x,y,u,v]/(xy-uv) is a normal domain

Let A= k[x,y,u,v]/(xy=uv), is this ring normal (integral closed in its field of fraction)?

Edit (see comments below): Because p is of height 1, then there exists one among x,y,u,v, say x such that f(x)\notin p for any f(x)\in k[x]. Otherwise, if there are polynomials in one variable for each of the variables x,y,u,v, contained in p, then p is of height >1. Thus f(x) becomes invertible in A_p for any f(x)\in k[x].