Joelene wanted to find the area of her rectangular back yard. She measured the length of the yard as 21 m and the width as 9 m.
Later, the actual dimensions of the yard were more accurately measured as 20.8 m and 9.2 m.

What is the relative error in her area calculation to the nearest thousandth?

A.) 0.012
B.) 0.013
C.) 0.015
D.) 0.018