Arectangle has an area of (x^2-17x+72) square units. since the areas of the rectangle is determined using the formula, a=lw, what could be the length and width of the rectangle?

a: length= (x-8) units and width = (x-9) units
b: length = (x+9) units and width = (x+8) units
c: length = (x-6) units and width = ( x-12) units
d: length = (x =12) units and width = (x +6) units