Laws of Probability and a Trihybrid Cross

Suppose we cross a trihybrid with purple flowers, and yellow round seeds (heterozygous for all three) with a plant with purple flowers and green, wrinkled seeds (heterozygous for flower color but homozygouse recessive for the other two characters).

Using Mendelian genetics, where the cross is PpYyRr x Ppyyrr, what fraction of...

Laws of Probability and a Trihybrid Cross