i am not really good at biology but i guess if we consider the fathers to be heterozygous and homozygous recessive then we would only get a population with half recessive and half heterozygous which can't be the case here so the only solution is to consider the case of both heterozygous fathers this would get us a number if homozygote dominant = homozygote recessive = 16 adding both recessive and dominant = 32 then we have 400 -32 = 368 this i guess is the number of people who are heterozygous but i don't study biology so you have to double check :)
