Don't mind my work but can someone give the answer for 50

I think that the answer is 240 square feet
so, first you divide the shapes in 2d shapes
       
area of the two triangle = 2 x b x h/2
                                      = 2 x 12 x 5/2
                                      =60 square feet

area of base = 12 x 6 = 72 square feet

area of rectangle = 5 x 6
                               = 30 square feet
area of 2nd rectangle = 13 x 6
                                  = 78 square feet 
 60 + 72 + 30 + 78 = 240 square feet

It would take her 20 minutes.