sproti

This problem is written in my language (not english) so I'll try to translate it the best I can. I've spend the last hour trying to figure this out but I just can't understand this problem. ------------------- The fungi S. cerevisiae creates tetrad spores. How high of a ratio can be expected of tetrad spores with tetratype (both parental types and recombinants) if there are 14 map units between genes? A. 7% B. 14% C. 28% D.72% E. 86% ------------------- So I assume what they mean is basicly among PD (Parental ditype), NPD (Nonparental ditype) and T (Tetratype) what ratio of tetrad spores has the tetrad type. I understand that the tetrad type itself will have parental types of 86% (43% each) and recombinants will have 14% (7% each) but I have no idea how I figure out the ratio of tetratypes.