A company offers a basic life insurance policy to its employees, as well as a supplemental life insurance policy. To purchase the supplemental policy, an employee must first purchase the basic policy. Let X denote the proportion of employees who purchase the basic policy, and Y the proportion of employees who purchase the supplemental policy. Let X and Y have the joint density function f(x, y) = 2(x + y) on the region where the density is positive. Given that 10% of the employees buy the basic policy, calculate the probability that fewer than 5% buy the supplemental policy.