Hi ! i have finished the (a) and (b). can you help me to Solve (c) i have confused about the Rule of 70

countrycode country year gappc pop AUS Australia 1820 826 334 Average annual Growth rate between 1820 and 2018=(49381/826)^1/198 -1=0.0209 AUS Australia 2018 49,831 24,855 AUS Australia 1990 27,373 16,956 Average annual Growth rate between between 1990 and 2018=(49831/27373)^1/28 -1=0.0216 CHN China 1820 882 381,000 CHN China 2018 13,102 1,385,439 Average annual Growth rate between between 1820 and 2018=(13102/882)^1/198-1=0.0137 CHN China 1990 2,982 1,135,185 Average annual Growth rate between between 1990and 2018=(13102/2982)^1/28-1=0.0543(a) Find the value of GDP per capita for Australia and China in 1820 and 2018. Calculate the average annual growth rate for the two countries (b) Find the value of GDP per capita for Australia and China in 1990. Calculate the average annual growth rate between 1990 and 2018 (c) Using the rule of 70, approximately how many years will it take for GDP per capita to double in Australia if GDP per capita growth continues at the 1990-2018 pace? How many years will it take for China's GDP per capita to double