Answer:
The sandy variation could be as a result of a homozygous recessive allele at one of two varying genes in these two different types of sandy pigs. Let's refer to them as genes A and B.
A kind of sandy pig may be aaBB and the variety AAbb. The F1 generation in this cross produces heterozygotes for both genes to give all red. This indicates that the A and B alleles are dominant. In the F2 generation, 6 out of 16 give us homozygous for either the aa or bb alleles and produces sandy.
Out of 16 will we have one that would be doubly homozygous and be white. The other 9 will possess at least one dominant allele for both genes.