In buying a car worth P 1,500,000 cash, the purchaser pays P 500,000 cash and agrees to pay the balance including interest at x % compounded semi - annually, by a sequence of 8 equal semiannual payments of P 178,118.98, the first due at the end of 4 years. Find x.

Select one: a. 4.8 b. 5.5 c. 6.3 d. 7.2