Joint Probability Density Function with Two Continuous Random Variables

Hi

Each front tire on a vehicle is supposed to be at a pressure of 26 psi. Suppose the actual air pressure is a rv in each tire: let x = right and y = left, with the joint pdf:

f(x,y) = K(x^2+y^2) 20<= x <= 30, 20<= y <= 30

0 otherwise

What is the value of K?

So the formula is the

double integral from 20 to 30 [k(x^2+y^2) dxdy

I solved it to get (2k * (38000/3)) , but to my surprise the solution showed this answer multiplied by 10.

Can anyone explain to me why I need to multiply by ten?