There is no solution since they are both adding $10 to their accounts every week.
The Kangaroo Rat and the common tree shrew is familiar because the kangaroo rat and the tree shrew have the same class: Mammalia, same phylum: Chordata, and the same kingdom : Animalia. They both are identical because they are small look like small rats etc.
a) 2/6 * 1/5 = 2/30 = 1/15
b) 1/15 + 2/6 * 1/5 = 2/15
