I am trying to find all integer solutions to Euler's totient function $\displaystyle \phi(3^x \cdot 5^y) = 600$

From a theorem in my book $\displaystyle \phi(n) = n(1 - 1/p1)(1- 1/p1)$

I get $\displaystyle 600 = 3^x\cdot5^y (2/3)(4/5)$

$\displaystyle 3^x\cdot5^y = 1125$

Now I am stuck because I dont know how to solve this, any suggestions?