Suppose that a life aged 30 arranged an insurance with the following parameters. If death occurs in the first 20 years, 10,000 is paid. Otherwise, 20,000 is paid. Moreover, it was arranged with the insurance company that a premium refund will be paid in the case of death during the first 5 years. This refund will be 25% of the net single premium. Assume that it holds: la 100- x, 0x 100 and i = 5%. Calculate the net single premium of this insurance.