$\\sum_{n=1}^{\\infty} 8 \\cdot (0.4)^{n-1}$

$\\sum_{n=1}^{\\infty} 10 \\cdot (0.3)^{n-1}$

$\\sum_{n=1}^{\\infty} 12 \\cdot (0.2)^{n-1}$

$\\sum_{n=1}^{\\infty} 6 \\cdot (0.5)^{n-1}$