The length of a rectangle is 4 units less than 5 times its width. The area of the rectangle is 197 square units. Which of the following equations can be used to find w, the width of the rectangle?
A. 
6w - 4 = 197
B. 
5w2 - 4w = 197
C. 
6w - 20 = 197
D. 
5w2 - 20w = 197