A female genotype, shown as abc / +++ produces 100 meiotic tetrads. Among these, 68 showed no cross over (NCO) events; 20 showed single crossover (SCO1) between a and b; 10 showed single crossover between b and c (SCO2) and 2 showed a double crossover (DCO) between a and b and between b and c. Of the 400 gametes produced, how many will be of the following types? Fill your answers in the table. (Source)
According to me, the answers should be,
A. $68\times4=272$
B. $20\times4=80$
C. $10\times4=40$
D. $2\times4=8$
However, the answers are $336, 40, 20, 4$ respectively. What am I getting wrong?