If ∑n=1∞arn−1=10\sum_{n=1}^{\infty} a r^{n-1} = 10∑n=1∞arn−1=10 and ∑n=1∞a2r2n−2=50\sum_{n=1}^{\infty} a^2 r^{2n-2} = 50∑n=1∞a2r2n−2=50, what is rrr?
0.50.50.5
0.40.40.4
0.80.80.8
0.20.20.2