The formula for a cylinder's surface area is : \(2\pi rh+2\pi { r }^{ 2 }\) in this question, h=x.
Let's plug the values in the formula
\(2\pi rh+2\pi { r }^{ 2 }\\ \\ 2\cdot \pi \cdot 6\cdot 8+2\cdot \pi \cdot { 6 }^{ 2 }=2\cdot 48\cdot \pi +2\cdot 36\cdot \pi =96\pi +72\pi =168\pi \quad \\ \\ 168\pi \quad square\quad units\\ Answer\quad is\quad A\)
