Answer:
90
Step-by-step explanation:
Length times with times height
$995.9....................... (ignore the dots)
Suppose the length of the triangle is x, if the perimeter of the rectangle is 100 ft, the width of the rectangle will be (50-x) ft.
Area of rectangle will be:
A=length*width
A=x(50-x)
A=50x-x^2
at maximum area, dA/dx=0
thus
dA/dx=50-2x=0
solving for x we get
2x=50
x=25
thus for maximum area length=25 ft
the size of the width will be
50-x=50-25=25 ft
thus the maximum area will be:
25*25=625 sq. feet
The lateral surface area of a cylinder is just the long side connecting the bases, whereas the total surface area includes both the lateral surface area and area of the two circular bases.

(Imagine a rectangle with the circumfrence of the base as one side and the height as the other being folded around)

(Plus the area of two circles)
The literal difference between surface areas would be the two bases 2πr² if you need that.