The Map of a Chromosome Interval Is: A--10 Mu--B--40 Mu--C

Multiple Choice

The map of a chromosome interval is: A--10 mu--B--40 mu--C
From the cross Abc / aBC * abc / abc, how many double crossovers would be expected out of 1000 progeny?

A) 5
B) 10
C) 20
D) 40
E) 80