Considering the following production function: $QKL,K,3KL,$ where $K$ denotes the amount $of$ capital used for production,

and $L$ the amount $of$ labour used. Which $of$ the sentences below best describes the production function?

The production function exhibits constant returns $to$ scale.

$We$ cannot tell with the information available.

The production function exhibits decreasing returns $to$ scale.

The production function exhibits increasing returns $to$ scale.