From the test cross (abc)(+++) x (abc)/(abc), where the parentheses indicate that the order of genes a, b & c is unknown, the following progeny were obtained.
Phenotype - Number
a++ 24
+b+ 69
++c 2
ab+ 4
a+c 75
+bc 20
abc 396
+++ 410
Indicate which allele is in the middle and explain how you arrived at your conclusion.