How do you find the surface area of each rectangular prism

Pls the last one and it has to be like number 6

Which diagram shows lines that must be parallel lines cut by transversal?

Cherie works in retail and her weekly salary includes commission for the amount she sells. the equation s=400+0.15c models the relation between her weekly salary, s, in dollars and the amount of her sales, c, in dollars. interpret the slope of the equation.