Question 99513
c=3X10^8 m/sec ... (2.1X10^18 m)/(3X10^8 m/sec)=7X10^9 sec


(60sec/min)(60min/hr)(24hr/day)(365day/yr)=3.16X10^7 sec/yr


(7X10^9 sec)/(3.16X10^7 sec/yr)=2.22X10^2 yr