If GCD(a,100)=5\text{GCD}(a, 100) = 5GCD(a,100)=5 and GCD(b,100)=10\text{GCD}(b, 100) = 10GCD(b,100)=10, what is GCD(a+b,100)\text{GCD}(a+b, 100)GCD(a+b,100)?
5
10
20
50