Table:
other crop
2001
2006
2011
2016

acres

fenugreek
179
284
414
2,809

spelt
6,939
10,886
10,526
15,958

quinoa
313
x
312
11,868

garlic
1,742
759
1,290
2,207

kale
65
75
92
448

sweet potato
162
759
1,418
1,776

sea buckthorn
.
206
333
520

Statement: crop area for sweet potatoes increased by 659 acres between 2006 and 2011.
Question: how many acres of crop area for sweet potates were increased between 2011 and 2006?
Answer: [659]