Please explain all steps. There are two firms. The first firm has the production function: $f(x,y)=$min$\{2x,x+y\}.$ The second firm has the production function $f(x,y)=x+$min$\{x,y\}.$

$($a$)$ On the graph below, use red ink to sketch a couple of production isoquants for the first firm at output levels: $y=10,$ and $y=40.$ Use black ink to sketch a couple of production isoquants for the second firm at output levels: $y=20,$ and $y=30.$

$($b$)$ Do either or both of these firms have constant returns to scale?